[mkgmap-dev] How to handle missing hgt files or fileswith voids?From Thomas Morgenstern webmaster at img2ms.de on Mon Jan 15 11:37:25 GMT 2018
For Europe is a good source for 1 sec. hgt EPSG 4326 : http://opendem.info/opendemeu_download_4326.html . Thomas -------------------------------------------------- Von: "Gerd Petermann" <gpetermann_muenchen at hotmail.com> Datum: Montag, 15. Januar 2018 08:55 An: "Development list for mkgmap" <mkgmap-dev at lists.mkgmap.org.uk> Betreff: Re: [mkgmap-dev] How to handle missing hgt files or fileswithvoids?> 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 at lists.mkgmap.org.uk> im Auftrag von > Henning Scholland <osm at 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 > > > > > > _______________________________________________ > mkgmap-dev mailing list > mkgmap-dev at lists.mkgmap.org.uk<mailto:mkgmap-dev at lists.mkgmap.org.uk> > http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev > > > > > _______________________________________________ > mkgmap-dev mailing list > mkgmap-dev at lists.mkgmap.org.uk > http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev >
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