Hi Gerd, The primary reason for the patch and hence the rules is to reduce the number of similar arcs warnings to a manageable number that are actually useful. A useful side effect is slightly reducing the size of the map. Many of the warnings are caused by highway areas overlapping linear highways. You are right that the patch does cause incorrect routing data - the first few I tried to route over seemed to be OK, but others failed, so I assume it is just luck when one still works. I can't find any NodCheck in the code, and with all warnings enabled, I don't see any messages relating to this. I was following your suggestion about using the code for --report-similar-arcs as a base to drop overlapping arcs. Checking back, I see you did mention you didn't know whether this would produce incorrect NOD data. I have realised I also need to delete the reverse arc and have added code for that, but haven't discovered how the NOD data is connected. Can you point me in the right direction? Don't suppose there is any documentation about the code structure... Cheers, Mike -----Original Message----- From: Gerd Petermann [mailto:gpetermann_muenchen@hotmail.com] Sent: 22 May 2021 06:31 To: Development list for mkgmap <mkgmap-dev@lists.mkgmap.org.uk> Subject: Re: [mkgmap-dev] Similar Arcs Hi Mike, what exactly is the benefit of those rules? What's the problem if the similar arcs are not removed? I can't belief that this works without causing possibly wrong routing data. Doesn't NodCheck complain about the removed arcs? Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Mike Baggaley <mike@tvage.co.uk> Gesendet: Samstag, 22. Mai 2021 00:51 An: 'Development list for mkgmap' Betreff: [mkgmap-dev] Similar Arcs Hi Gerd, Please find attached the patch for deleting similar arcs. It uses a new mkgmap:nooverlap tag which can be set to a number between 0 and 127 (default 0) in the lines file. If set to a number greater than zero then the overlapping part of the line will be deleted if it overlaps another line, providing the access of the other line is a superset of its access. If both lines have non zero values and have the same access then the line with the higher value will be deleted. In my style file I have the following: highway=service & (area=yes | mkgmap:mp_created=true) & (foot=yes | foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* | access=yes | access=permissive))) {set mkgmap:car=no; set mkgmap:bicycle=no; set foot=yes; set mkgmap:flare-check=no; set mkgmap:numbers=false; set mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none; set mkgmap:nooverlap=1} [0x13 road_class=0 road_speed=0 resolution 22] highway=pedestrian & (area=yes | mkgmap:mp_created=true) & (foot=yes | foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* | access=yes | access=permissive))) {set mkgmap:car=no; set mkgmap:bicycle=no; set foot=yes; set mkgmap:flare-check=no; set mkgmap:numbers=false; set mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none; set mkgmap:nooverlap=1} [0x0d road_class=0 road_speed=0 resolution 22] amenity=parking & (parking!=* | parking=surface) & (foot=yes | foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* | access=yes | access=permissive))) {set mkgmap:car=no; set mkgmap:bicycle=no; set foot=yes; set mkgmap:numbers=false; set mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none; set mkgmap:nooverlap=2; set mkgmap:delivery=no; set mkgmap:truck=no; set mkgmap:bus=no; set mkgmap:taxi=no; set mkgmap:emergency=no } [0x08 road_class=0 road_speed=0 resolution 24 continue] and similar for railway=platform, man_made=pier, man_made=jetty and leisure=slipway. Cheers, Mike

I thought that patch could be used to remove the dual highways at low resolutions. Does not seem to work for that with a value of 4... So it is only about routing, right? I will not work on lines but only roads? On Sun, 23 May 2021 at 20:02, Gerd Petermann < gpetermann_muenchen@hotmail.com> wrote:

Hi Mike,

the NodCheck (and NodDisplay is part of the display utility, see https://svn.mkgmap.org.uk/svn/display NodCheck reports lots of errors about angles and lengths of arcs which probably are not critical and mostly caused by rounding.

There are some pdf docs about the IMG format and also the wiki https://wiki.openstreetmap.org/wiki/OSM_Map_On_Garmin/NOD_Subfile_Format Some details are probably not documented, esp. the last findings about encoding of bearings.

I think it is possible to suppress some duplicate arcs, e.g. if two roads have the same first arc it should be possible to truncate one of the roads. It might be needed to remove all the data in RGN and NET as well, so that you simulate the removal of data in OSM. I don't see a need for this, the effect should be very small for styles which don't try to make objects like amenity=parking routable.

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Mike Baggaley <mike@tvage.co.uk> Gesendet: Sonntag, 23. Mai 2021 19:27 An: 'Development list for mkgmap' Betreff: Re: [mkgmap-dev] Similar Arcs

Hi Gerd,

The primary reason for the patch and hence the rules is to reduce the number of similar arcs warnings to a manageable number that are actually useful. A useful side effect is slightly reducing the size of the map. Many of the warnings are caused by highway areas overlapping linear highways. You are right that the patch does cause incorrect routing data - the first few I tried to route over seemed to be OK, but others failed, so I assume it is just luck when one still works. I can't find any NodCheck in the code, and with all warnings enabled, I don't see any messages relating to this. I was following your suggestion about using the code for --report-similar-arcs as a base to drop overlapping arcs. Checking back, I see you did mention you didn't know whether this would produce incorrect NOD data. I have realised I also need to delete the reverse arc and have added code for that, but haven't discovered how the NOD data is connected. Can you point me in the right direction? Don't suppose there is any documentation about the code structure...

Cheers, Mike

-----Original Message----- From: Gerd Petermann [mailto:gpetermann_muenchen@hotmail.com] Sent: 22 May 2021 06:31 To: Development list for mkgmap <mkgmap-dev@lists.mkgmap.org.uk> Subject: Re: [mkgmap-dev] Similar Arcs

Hi Mike,

what exactly is the benefit of those rules? What's the problem if the similar arcs are not removed? I can't belief that this works without causing possibly wrong routing data. Doesn't NodCheck complain about the removed arcs?

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Mike Baggaley <mike@tvage.co.uk> Gesendet: Samstag, 22. Mai 2021 00:51 An: 'Development list for mkgmap' Betreff: [mkgmap-dev] Similar Arcs

Hi Gerd,

Please find attached the patch for deleting similar arcs. It uses a new mkgmap:nooverlap tag which can be set to a number between 0 and 127 (default 0) in the lines file. If set to a number greater than zero then the overlapping part of the line will be deleted if it overlaps another line, providing the access of the other line is a superset of its access. If both lines have non zero values and have the same access then the line with the higher value will be deleted.

In my style file I have the following:

highway=service & (area=yes | mkgmap:mp_created=true) & (foot=yes | foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* | access=yes | access=permissive))) {set mkgmap:car=no; set mkgmap:bicycle=no; set foot=yes; set mkgmap:flare-check=no; set mkgmap:numbers=false; set mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none; set mkgmap:nooverlap=1} [0x13 road_class=0 road_speed=0 resolution 22]

highway=pedestrian & (area=yes | mkgmap:mp_created=true) & (foot=yes | foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* | access=yes | access=permissive))) {set mkgmap:car=no; set mkgmap:bicycle=no; set foot=yes; set mkgmap:flare-check=no; set mkgmap:numbers=false; set mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none; set mkgmap:nooverlap=1} [0x0d road_class=0 road_speed=0 resolution 22]

amenity=parking & (parking!=* | parking=surface) & (foot=yes | foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* | access=yes | access=permissive))) {set mkgmap:car=no; set mkgmap:bicycle=no; set foot=yes; set mkgmap:numbers=false; set mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none; set mkgmap:nooverlap=2; set mkgmap:delivery=no; set mkgmap:truck=no; set mkgmap:bus=no; set mkgmap:taxi=no; set mkgmap:emergency=no } [0x08 road_class=0 road_speed=0 resolution 24 continue]

and similar for railway=platform, man_made=pier, man_made=jetty and leisure=slipway.

Cheers, Mike

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