DEM File Format and mkgmap
Hi all, I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon. Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here. For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903) Gerd
Hi Gerd Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'? Would be great if you could compile the DemDisplay.java so we can do ome testing as well. I'm glad you are almost 'getting there'! r Nick On 03/12/2017 11:16, Gerd Petermann wrote:
Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Nick, My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now. A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile . Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'? Would be great if you could compile the DemDisplay.java so we can do ome testing as well. I'm glad you are almost 'getting there'! r Nick On 03/12/2017 11:16, Gerd Petermann wrote:
Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Many thanks Gerd Will have a go at it today and let you know my findings, if any ! Nick On 04/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote:
Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Nick, I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now... Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Many thanks Gerd Will have a go at it today and let you know my findings, if any ! Nick On 04/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote:
Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Gerd Thanks for letting me know That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar r Nick On 04/12/2017 13:49, Gerd Petermann wrote:
Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote:
Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Gerd I think all the dem files from the very old GBTopo can only be parsed up to a certain point I've included 3 excmples with tre http://files.mkgmap.org.uk/download/362/00145336.zip Nick On 04/12/2017 15:02, osm@pinns wrote:
Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote:
Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote:
Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532)
at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831)
at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Nick, yes, I know that. I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd I think all the dem files from the very old GBTopo can only be parsed up to a certain point I've included 3 excmples with tre http://files.mkgmap.org.uk/download/362/00145336.zip Nick On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd Thanks for letting me know That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar r Nick On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick, I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now... Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Many thanks Gerd Will have a go at it today and let you know my findings, if any ! Nick On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick, My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now. A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile . Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'? Would be great if you could compile the DemDisplay.java so we can do ome testing as well. I'm glad you are almost 'getting there'! r Nick On 03/12/2017 11:16, Gerd Petermann wrote: Hi all, I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon. Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here. For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903) Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi all, I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Nick, yes, I know that. I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd I think all the dem files from the very old GBTopo can only be parsed up to a certain point I've included 3 excmples with tre http://files.mkgmap.org.uk/download/362/00145336.zip Nick On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd Thanks for letting me know That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar r Nick On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick, I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now... Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Many thanks Gerd Will have a go at it today and let you know my findings, if any ! Nick On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick, My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now. A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile . Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'? Would be great if you could compile the DemDisplay.java so we can do ome testing as well. I'm glad you are almost 'getting there'! r Nick On 03/12/2017 11:16, Gerd Petermann wrote: Hi all, I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon. Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here. For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903) Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Gert I think I may have a dem that causes a problem http://files.mkgmap.org.uk/download/364/12345684.zip C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875) It is part of OSM Greece r Nick On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Nick, yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Gert I think I may have a dem that causes a problem http://files.mkgmap.org.uk/download/364/12345684.zip C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875) It is part of OSM Greece r Nick On 05/12/2017 10:17, Gerd Petermann wrote: Hi all, I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Nick, yes, I know that. I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd I think all the dem files from the very old GBTopo can only be parsed up to a certain point I've included 3 excmples with tre http://files.mkgmap.org.uk/download/362/00145336.zip Nick On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd Thanks for letting me know That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar r Nick On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick, I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now... Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Many thanks Gerd Will have a go at it today and let you know my findings, if any ! Nick On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick, My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now. A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile . Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'? Would be great if you could compile the DemDisplay.java so we can do ome testing as well. I'm glad you are almost 'getting there'! r Nick On 03/12/2017 11:16, Gerd Petermann wrote: Hi all, I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon. Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here. For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903) Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Gerd Excellent, will do so more hunting! Nick On 05/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Gert
I think I may have a dem that causes a problem
http://files.mkgmap.org.uk/download/364/12345684.zip
C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875)
It is part of OSM Greece
r
Nick
On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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Hi Nick, you can stop for a while. With the data from Andreas I have enough special cases for now. Please wait for a new DemDisplay version. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 14:33:14 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Excellent, will do so more hunting! Nick On 05/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Gert
I think I may have a dem that causes a problem
http://files.mkgmap.org.uk/download/364/12345684.zip
C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875)
It is part of OSM Greece
r
Nick
On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
OK , with r508 I fixed the problems that showed up in the files from Nick and Andreas, bot were related to the meaning of header info. I've also changed the program so that it doesn't produce so much output unless option --verbose is given as 1st arg to speed up the error hunt ;-) See http://files.mkgmap.org.uk/download/366/display.jar Unfortunately it still fails to read all Garmin demo files. Obviously the prediction implemented in DemDisplay is not always in sync with Garmins algo. Maybe this is related to the fact that Garmin maps use values in feet instead of metres. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 14:33:14 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Excellent, will do so more hunting! Nick On 05/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Gert
I think I may have a dem that causes a problem
http://files.mkgmap.org.uk/download/364/12345684.zip
C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875)
It is part of OSM Greece
r
Nick
On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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Hi Andreas, thanks for that. fixed with r509: http://files.mkgmap.org.uk/download/368/display.jar Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von andreas.schmidt.hetschbach@t-online.de <andreas.schmidt.hetschbach@t-online.de> Gesendet: Mittwoch, 6. Dezember 2017 13:10:52 An: mkgmap-dev; Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd, added http://files.mkgmap.org.uk/detail/367 which cause C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710081\63710081.DEM 1>63710081\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946) C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710082\63710082.DEM 1>63710082\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946) regards Andreas Gesendet von Mail<https://go.microsoft.com/fwlink/?LinkId=550986> für Windows 10 Von: Gerd Petermann<mailto:gpetermann_muenchen@hotmail.com> Gesendet: Mittwoch, 6. Dezember 2017 10:52 An: Development list for mkgmap<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap OK , with r508 I fixed the problems that showed up in the files from Nick and Andreas, bot were related to the meaning of header info. I've also changed the program so that it doesn't produce so much output unless option --verbose is given as 1st arg to speed up the error hunt ;-) See http://files.mkgmap.org.uk/download/366/display.jar Unfortunately it still fails to read all Garmin demo files. Obviously the prediction implemented in DemDisplay is not always in sync with Garmins algo. Maybe this is related to the fact that Garmin maps use values in feet instead of metres. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 14:33:14 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Excellent, will do so more hunting! Nick On 05/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Gert
I think I may have a dem that causes a problem
http://files.mkgmap.org.uk/download/364/12345684.zip
C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875)
It is part of OSM Greece
r
Nick
On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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Hi Gerd have just done Nepal area with Himalayas - thanks to the new display.jar it's much quicker to check But, no issues found with the latest display.jar, except it has highlighted one major issue creating DEM files. At one stage using Franks program I was told there were 443977 tiles to be created - after five minutes it seemed to trickle to 1 tile a second - on that basis it would take all day ! I resplit the pfb using small maxnodes; this halved the number of tiles to 270000 and only used 1 layer- but even that took 40 mins. I have a suspicion that most people only want to create dem files on the hoof when the time penalty is acceptable. You can always create one off maps containing only say contours and dem data. This might have some relevance if , when (!) mkgmap is capable of creating dem files. Nick On 06/12/2017 13:55, Gerd Petermann wrote:
Hi Andreas,
thanks for that. fixed with r509: http://files.mkgmap.org.uk/download/368/display.jar
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von andreas.schmidt.hetschbach@t-online.de <andreas.schmidt.hetschbach@t-online.de> Gesendet: Mittwoch, 6. Dezember 2017 13:10:52 An: mkgmap-dev; Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd,
added http://files.mkgmap.org.uk/detail/367 which cause
C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710081\63710081.DEM 1>63710081\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946)
C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710082\63710082.DEM 1>63710082\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946)
regards
Andreas
Gesendet von Mail<https://go.microsoft.com/fwlink/?LinkId=550986> für Windows 10
Von: Gerd Petermann<mailto:gpetermann_muenchen@hotmail.com> Gesendet: Mittwoch, 6. Dezember 2017 10:52 An: Development list for mkgmap<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
OK , with r508 I fixed the problems that showed up in the files from Nick and Andreas, bot were related to the meaning of header info. I've also changed the program so that it doesn't produce so much output unless option --verbose is given as 1st arg to speed up the error hunt ;-) See http://files.mkgmap.org.uk/download/366/display.jar
Unfortunately it still fails to read all Garmin demo files. Obviously the prediction implemented in DemDisplay is not always in sync with Garmins algo. Maybe this is related to the fact that Garmin maps use values in feet instead of metres.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 14:33:14 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Excellent, will do so more hunting!
Nick
On 05/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Gert
I think I may have a dem that causes a problem
http://files.mkgmap.org.uk/download/364/12345684.zip
C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875)
It is part of OSM Greece
r
Nick
On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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Hi Nick, I think Frank already pointed out that his code is not much optimized for speed. The same is true for DemDisplay. Once DemDisplay is able to read all DEM files I'll start looking at the conversion from HGT format into DEM format. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Mittwoch, 6. Dezember 2017 19:39:33 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd have just done Nepal area with Himalayas - thanks to the new display.jar it's much quicker to check But, no issues found with the latest display.jar, except it has highlighted one major issue creating DEM files. At one stage using Franks program I was told there were 443977 tiles to be created - after five minutes it seemed to trickle to 1 tile a second - on that basis it would take all day ! I resplit the pfb using small maxnodes; this halved the number of tiles to 270000 and only used 1 layer- but even that took 40 mins. I have a suspicion that most people only want to create dem files on the hoof when the time penalty is acceptable. You can always create one off maps containing only say contours and dem data. This might have some relevance if , when (!) mkgmap is capable of creating dem files. Nick On 06/12/2017 13:55, Gerd Petermann wrote:
Hi Andreas,
thanks for that. fixed with r509: http://files.mkgmap.org.uk/download/368/display.jar
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von andreas.schmidt.hetschbach@t-online.de <andreas.schmidt.hetschbach@t-online.de> Gesendet: Mittwoch, 6. Dezember 2017 13:10:52 An: mkgmap-dev; Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd,
added http://files.mkgmap.org.uk/detail/367 which cause
C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710081\63710081.DEM 1>63710081\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946)
C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710082\63710082.DEM 1>63710082\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946)
regards
Andreas
Gesendet von Mail<https://go.microsoft.com/fwlink/?LinkId=550986> für Windows 10
Von: Gerd Petermann<mailto:gpetermann_muenchen@hotmail.com> Gesendet: Mittwoch, 6. Dezember 2017 10:52 An: Development list for mkgmap<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
OK , with r508 I fixed the problems that showed up in the files from Nick and Andreas, bot were related to the meaning of header info. I've also changed the program so that it doesn't produce so much output unless option --verbose is given as 1st arg to speed up the error hunt ;-) See http://files.mkgmap.org.uk/download/366/display.jar
Unfortunately it still fails to read all Garmin demo files. Obviously the prediction implemented in DemDisplay is not always in sync with Garmins algo. Maybe this is related to the fact that Garmin maps use values in feet instead of metres.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 14:33:14 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Excellent, will do so more hunting!
Nick
On 05/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Gert
I think I may have a dem that causes a problem
http://files.mkgmap.org.uk/download/364/12345684.zip
C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875)
It is part of OSM Greece
r
Nick
On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
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Hi Andreas, thanks for your feedback. I think that means that DemDisplayr509 works with DEM files produced by Franks program. Still, it doesn't seem to work with most Garmin files, at least none which have the values coded in feet. Right now I am looking at a file which works fine for zoom level 0 and almost immediatly causes trouble in zoom level 1. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von andreas.schmidt.hetschbach@t-online.de <andreas.schmidt.hetschbach@t-online.de> Gesendet: Donnerstag, 7. Dezember 2017 10:58:39 An: mkgmap-dev; Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd, checked * Germany * Mallorca * Sweden without any fault. Although for now it is some manual work (produce the DEM-files with Franks program, correct the tdb-file and so on), the results showed up in basecamp (3d) and Oregon600 (hillshading) are such amazing. I´m really looking forward getting it integrated into the mkgmap-process by you. Great work! Andreas Gesendet von Mail<https://go.microsoft.com/fwlink/?LinkId=550986> für Windows 10 Von: Gerd Petermann<mailto:gpetermann_muenchen@hotmail.com> Gesendet: Mittwoch, 6. Dezember 2017 14:55 An: Development list for mkgmap<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Andreas, thanks for that. fixed with r509: http://files.mkgmap.org.uk/download/368/display.jar Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von andreas.schmidt.hetschbach@t-online.de <andreas.schmidt.hetschbach@t-online.de> Gesendet: Mittwoch, 6. Dezember 2017 13:10:52 An: mkgmap-dev; Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd, added http://files.mkgmap.org.uk/detail/367 which cause C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710081\63710081.DEM 1>63710081\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946) C:\Garmin\FAMILY_6371.gmap\Product1>(java -ea -Xmx1000m -cp c:\garmin\bin\display.jar;c:\garmin\bin\mkgmap.jar test.display.DemDisplay 63710082\63710082.DEM 1>63710082\dem_decode.txt ) Exception in thread "main" java.lang.ArithmeticException: / by zero at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:862) at test.display.DemDisplay.readFileHeader(DemDisplay.java:925) at test.display.DemDisplay.print(DemDisplay.java:882) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:946) regards Andreas Gesendet von Mail<https://go.microsoft.com/fwlink/?LinkId=550986> für Windows 10 Von: Gerd Petermann<mailto:gpetermann_muenchen@hotmail.com> Gesendet: Mittwoch, 6. Dezember 2017 10:52 An: Development list for mkgmap<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap OK , with r508 I fixed the problems that showed up in the files from Nick and Andreas, bot were related to the meaning of header info. I've also changed the program so that it doesn't produce so much output unless option --verbose is given as 1st arg to speed up the error hunt ;-) See http://files.mkgmap.org.uk/download/366/display.jar Unfortunately it still fails to read all Garmin demo files. Obviously the prediction implemented in DemDisplay is not always in sync with Garmins algo. Maybe this is related to the fact that Garmin maps use values in feet instead of metres. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 14:33:14 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap Hi Gerd Excellent, will do so more hunting! Nick On 05/12/2017 13:27, Gerd Petermann wrote:
Hi Nick,
yes, that one was special because it contained 4 byte offsets. DemDisplay r507 supports only up to 3 bytes. Fixed soon.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Dienstag, 5. Dezember 2017 13:33:16 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Gert
I think I may have a dem that causes a problem
http://files.mkgmap.org.uk/download/364/12345684.zip
C:\Users\Owner\Desktop\mkgmap-r3997>java -cp display.jar;mkgmap.jar test.display .DemDisplay 12345684.DEM 1>log12345684.txt Exception in thread "main" java.lang.RuntimeException: did not read all avalaibl e bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:4 98) at test.display.DemDisplay$DemSection.decodeBitstreams(DemDisplay.java:8 02) at test.display.DemDisplay.readFileHeader(DemDisplay.java:859) at test.display.DemDisplay.print(DemDisplay.java:816) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:875)
It is part of OSM Greece
r
Nick
On 05/12/2017 10:17, Gerd Petermann wrote:
Hi all,
I've changed my strategy now. I've modified DemDisplay to display the decoded height together with lat/lon. If a new value differs by more than a few meters from the value left or above it is probably wrong. Hope this helps me to find the remaining special cases.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> Gesendet: Dienstag, 5. Dezember 2017 09:26:37 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Nick, yes, I know that.
I've fixed some problem in DemDisplay, so here is r507: http://files.mkgmap.org.uk/download/363/display.jar
It seems I was not clear about my strategy. I am searching for DEM files created by Franks program which display tool cannot parse. Please don't post data from Garmin if that doesn't come from free demo maps. I have quite a few DEM files from those demo maps, but the problem with that data is that I don't know for sure what values they contain. If you find a DEM produced by Franks program which r507 still cannot read I need the options for BuildDEMFile and the *.TRE file so that I can reproduce the DEM file and finally trace what values Franks program creates. With a bit of luck this will help to fix the problems with the demo data.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 16:27:20 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
I think all the dem files from the very old GBTopo can only be parsed up to a certain point
I've included 3 excmples with tre
http://files.mkgmap.org.uk/download/362/00145336.zip
Nick
On 04/12/2017 15:02, osm@pinns wrote: Hi Gerd
Thanks for letting me know
That is probably why eventually it stopped with repeated plateau len 64 messages on one of the dems builddemfile created
I have some 'old' non nt Garmin Topo maps with dem and will have a go using your display.jar
r
Nick
On 04/12/2017 13:49, Gerd Petermann wrote: Hi Nick,
I just found out that display tool can not yet read DEM tiles with multiple zoom levels. Working on it now...
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 14:35:15 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Many thanks Gerd
Will have a go at it today and let you know my findings, if any !
Nick
On 04/12/2017 13:27, Gerd Petermann wrote: Hi Nick,
My understanding is that the prediction starts with the values from the header (min and max height in the tile) The first row is indeed rather easy to decode. Frank has described many more details in his pdf, and his program seems to create valid DEM data since Basecamp displays it, I just try to reduce the number of special cases now.
A compiled display.jar r505 is here: http://files.mkgmap.org.uk/download/361/display.jar If you also download and unzip this mkgmap package http://www.mkgmap.org.uk/download/mkgmap-r3997.zip you can run e.g. java -cp display.jar;mkgmap-r3997\mkgmap.jar test.display.DemDisplay 12345678.DEM > log.txt
I am interested in those files created by BuildDemFile which create a run time exception. If you find one or more, I need the original *.TRE file(s) which were the input for BuildDemFile .
Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk><mailto:osm@pinns.co.uk> Gesendet: Montag, 4. Dezember 2017 13:00:27 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] DEM File Format and mkgmap
Hi Gerd
Presumably some hgt data gets stored in a tile from which other data is predicted? Perhaps the first 'row'?
Would be great if you could compile the DemDisplay.java so we can do ome testing as well.
I'm glad you are almost 'getting there'!
r
Nick
On 03/12/2017 11:16, Gerd Petermann wrote: Hi all,
I think I understand now much more about this format. I used Frank Stinners code for BuildDEMFile and his pdf to write a decoder in the display tool. I still fails to read some Garmin DEM files but seems to work with the files produced by BuildDEMFile. My current work flow is to generate DEM files with BuildDEMFile and read them with my decoder. If the decoder fails I can find out why because I can trace step by step what BuildDEMFile does. I guess that I did not yet hit all special cases identified by Frank, but I am making good progress now, so I hope I'll be able to start implementing a DEM encoder in mkgmap soon.
Reg. the format: It is quite different to those used in other GARMIN sub files like NOD, NET, RGN etc. In short: The data is organized in tiles, typically 64*64 values. Instead of storing each value Garmin uses some statistics to predict the next value based on the already processed values. This predicted value is subtracted from the real value and only the delta is stored. The better the prediction, the closer to 0 is the delta. The prediction also calculates the error-probability of the prediction and uses this to select the number of bits which are needed to store the value. If the delta is larger than expected the so called BigBin encoding is used. The format to store the delta is optimized for values close to 0, so that many deltas are stored with only 1 or 2 bits. A 2nd trick to save space is to use run length encoding for repeated values. So, the tricky part is to find out exactly how the prediction algo by Garmin works. Frank has done really great work here.
For those who want to try the display tool: You have to compile on your own and you also need an installed mgkmap.jar. If that is available a command like this (replace d:\... with your paths) should produce a large txt file: java -ea -Xmx1000m -cp d:\display\dist\display.jar;d:\mkgmap\dist\mkgmap.jar test.display.DemDisplay test.DEM > dem_decode.txt
I am now searching for DEM files produced by BuildDEMFile which are not properly processed by display tool. When it fails you'll see a traceback like this Exception in thread "main" java.lang.RuntimeException: did not read all avalaible bytes at test.display.DemDisplay$DemTile.decodeBitStreamData(DemDisplay.java:532) at test.display.DemDisplay$DemSection.decodeBitstream(DemDisplay.java:831) at test.display.DemDisplay.readFileHeader(DemDisplay.java:887) at test.display.DemDisplay.print(DemDisplay.java:845) at test.display.CommonDisplay.display(CommonDisplay.java:171) at test.display.CommonDisplay.display(CommonDisplay.java:196) at test.display.DemDisplay.main(DemDisplay.java:903)
Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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Hi Gerd,
Right now I am looking at a file which works fine for zoom level 0 and almost immediatly causes trouble in zoom level 1.
Some time ago I was trying to split DEM levels and it didn't work for me. I have assumed, that DEM layers aren't independent. My guess is, that in some cases one layer could have references to another layer. I didn't notice description of that kind of references in Frank's document, but I didn't read it thoroughly enough to be sure. -- Best regards, Andrzej
participants (5)
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andreas.schmidt.hetschbach＠t-online.de -
Andrzej Popowski -
Gerd Petermann -
Gerd Petermann
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osm＠pinns