Hi all, replied to David instead of the list... See below Gerd ________________________________________ Von: Gerd Petermann <gpetermann_muenchen@hotmail.com> Gesendet: Donnerstag, 25. Januar 2018 18:08 An: Pazapas Betreff: AW: [mkgmap-dev] How to handle missing hgt files or files with voids? Hi all, see http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4089 and http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4090 @David: You are free to use any source, the program will always try to read hgt data. This is only about the message that is produced when a hgt file is not found. With 4090 you will see a list of files that were not found although we know that hgt info exists. Hope that makes it clearer now? Gerd ________________________________________ Von: Pazapas <pazapas@orange.fr> Gesendet: Donnerstag, 25. Januar 2018 17:38 An: Gerd Petermann Betreff: Re: [mkgmap-dev] How to handle missing hgt files or files with voids? Hello, Why a list of missing hgt is needed ? I would prefer that mkgmap adds itself avirtual void tile and writes a warning in console or output a report of the compilation in a text file. We then are free to use any sourc of custom hgt files. Again, chapeau bas for all your work, David Pazapas

Le 25 janv. 2018 à 13:11, Gerd Petermann <gpetermann_muenchen@hotmail.com> a écrit :

Hi Nick,

I think it is not a matter of speed, the file is only read once. I think I'll keep the human readable format, the size of mkgmap.jar probably doesn't matter much.

Reg. --dem-interpolation see http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4087

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Donnerstag, 25. Januar 2018 13:03 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] How to handle missing hgt files or files with voids?

Hi Gerd

A binary file sounds very 'Garminesque' and if its a matter of speed then I would prefer such a format -

btw has the --dem-interpolation option been implemented yet ?

Nick

On 25/01/2018 11:59, thesurveyor@wolke7.net<mailto:thesurveyor@wolke7.net> wrote: Hi Gerd,

first many thanks for your work on mkgmap.

for the list of available hgt files: I prefer a human readable format

Regards, Gert

Gesendet: Donnerstag, 25. Januar 2018 um 12:40 Uhr Von: "Gerd Petermann" <gpetermann_muenchen@hotmail.com><mailto:gpetermann_muenchen@hotmail.com> An: "Development list for mkgmap" <mkgmap-dev@lists.mkgmap.org.uk><mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] How to handle missing hgt files or files with voids? Hi all,

I've played with the list of available hgt files created by Henning. I've coded a reader for the list so that mkgmap can check if a missing hgt file should exist or if it covers ocean. The idea is to print a warning if a file was not found when it should be. The check is fast, but the list is long, so I wonder if I should store it "as is" in the mkgmap binary like we do with LocatorConfig.xml or if I should use another format. The most obvious for me would be a binary file containing 180*360 bits, a 1 bit for every file that should exist.

What do you think?

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: Montag, 15. Januar 2018 14:25 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] How to handle missing hgt files or files with voids?

Hi Henning,

I'll see if I can use srtm.zip. I think voids are interesting. When I started coding DEM support I searched my PC for *.hgt files and found them in several places. Later I found out that some of those files have voids and that better data exists (assuming that files without voids have fewer errors) So, I think it would be good to have a list of those files that have voids.

I'll see what is needed for this.

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Henning Scholland <osm@hscholland.de><mailto:osm@hscholland.de> Gesendet: Montag, 15. Januar 2018 12:21:09 An: mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] How to handle missing hgt files or files with voids?

This would be the list of all hgt-files available on viewfinder.

In each zip-file of viewfinder there are 6° in E-W direction and 3° in N-S. The scheme of naming is also simple. That list I also attached.

In general I think it's better to just output a list, which hgt-files/viefinder-tiles are missing than writing a downloader. I mean in total it's 13GB of data. If you need to download it manually, you are more aware of what you are doing and not just download them all.

Regarding voids: I think if there is a possibility the user can fix the hgt file, A list can be helpful. Otherwise I don't know if a list would be helpful. Only use case I see is to ask the user to use better data. But then we need a list, which source is best in which area. And finally all the different sources need to match each other. Otherwise it will lead to a hard border between 2 sources. I think this will be much to complicated...

Maybe for advanced users there can be a Warning message, hgt-file N00E100.hgt contains 3 voids. So user can compare different sources manually.

Henning

...

On 15.01.2018 16:55, Gerd Petermann wrote: Hi Henning,

checking data is not that easy, but I'll think about that option.

I'd like to add a short howto that describes ways to get good hgt data, but I don't know any method for Windows users. phyghtmap is good, but installation on Win is complex and doc for that looks out-aged. Srtm2Osm seems out-dated, as well as Groundtruth.

So, up to now I try to guess what areas I have to download from viewfinder. Any hints ?

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Henning Scholland <osm@hscholland.de><mailto:osm@hscholland.de> Gesendet: Montag, 15. Januar 2018 09:05:24 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] How to handle missing hgt files or files with voids?

Hi Gerd,

regarding 1) I can create a list of existing tiles of Viewfinder (which covers all land area so far I see). But it will be a long list. I remember it's about 25000 files in total. So maybe it's easier to create a polygon or at least take the list and let software create the polygon. An easier way can be to check if data is available. No data might be sea. Of course it's not 100% sure, as there are deserts and ferries.

Another idea I had during the weekend was to output a osm-file with missing areas. So then user can check. But I came to conclusion, that it's easily visible in the map later. So I'm not sure it's useful at all.

Henning

On 2018-01-15 15:45, Gerd Petermann wrote:

Hi all,

1) The current code (only) writes a log message with severity WARNING for a missing hgt file: "file xxx.hgt not found. Is expected to cover sea." I wonder if we can create a list of files that can exist or maybe a polygon that can be tested so that tiles which are knwon to cover land are reported as errors. When you look at http://viewfinderpanoramas.org/Coverage%20map%20viewfinderpanoramas_org3.htm you can see that such a polygon would be quite complex. Did anybody already try to define such a polygon or list of files that would cover only ocean?

2) Should mkgmap print a warning when voids in the hgt file(s) have an influence on the DEM data? I think yes, but it is a bit more complex to measure the real effect. Reason: We read the 4 hgt values next to the wanted DEM point and use interpolation to calculate the height that is stored in the DEM file. If one or two of the 4 points are voids they may still have no influence if the wanted point is very close to one that is not a void. Another problem is that a single void might be used several times. So, another option would be to add an option like --dem-check-hgt which could read all existing hgt files and report the number of voids for each. I'd prefer this because it would have no impact on performance for normal processing. Or maybe there is already a tool for this that works on all platforms (win,linux,mac) ?

Comments?

Gerd

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