[mkgmap-dev] "Small" SRTM1 files and DEM maps

Thu Apr 16 10:31:52 BST 2020

Hi Carlos,

so your conversion routine is wrong. The file size is 12.970.802 bytes. There is no integer n for which 2 * n^2 results in this value.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Carlos Dávila <cdavilam at orangecorreo.es>
Gesendet: Donnerstag, 16. April 2020 11:19
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] "Small" SRTM1 files and DEM maps

Hi Gerd
Forgot to mention files are downloaded as geotiff, but I then convert
them to hgt, sorry.
You can download a sample one from
https://alternativaslibres.org/tmp/N50E118.hgt

El 16/4/20 a las 9:18, Gerd Petermann escribió:
> Hi Carlos,
>
> are you talking about geotiff format? I think someone documented how that format can be converted to *.hgt.
> Can you post a link to such a file?
>
> Gerd
>
>
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Carlos Dávila <cdavilam at orangecorreo.es>
> Gesendet: Montag, 13. April 2020 14:08
> An: mkgmap-dev at lists.mkgmap.org.uk
> Betreff: Re: [mkgmap-dev] "Small" SRTM1 files and DEM maps
>
> Hi Gerd
> They are downloaded by phyghtmap. This is what I found digging into
> phyghtmap files:
> |def getSRTMFileServer(self, resolution, srtmVersion):||
> ||        if srtmVersion == 2.1:||
> ||            return
> "https://dds.cr.usgs.gov/srtm/version2_1/SRTM{0:d}".format(resolution)||
> ||        elif srtmVersion == 3.0:||
> ||            if resolution == 1:||
> ||                urlRe =
> "https://earthexplorer.usgs.gov/download/8360/SRTM1{:s}V3/GEOTIFF/EE"||
> ||            elif resolution == 3:||
> ||                urlRe =
> "https://earthexplorer.usgs.gov/download/4960/SRTM3{:s}V2/GEOTIFF3/EE"||
> ||            return urlRe|
> They should come from the second URL above.
>
> El 13/4/20 a las 8:24, Gerd Petermann escribió:
>> Hi Carlos,
>>
>> sorry for the late response. I found no hint on the phyghtmap page http://katze.tfiu.de/projects/phyghtmap/
>> regarding a new format for srtm data. The hgt format is not compressed. Do you know from where these 12.4 MB files came from?
>>
>> Gerd
>>
>> ________________________________________
>> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Carlos Dávila <cdavilam at orangecorreo.es>
>> Gesendet: Samstag, 11. April 2020 17:09
>> An: Development list for mkgmap
>> Betreff: [mkgmap-dev] "Small" SRTM1 files and DEM maps
>>
>> I use phyghtmap to build contour lines and also to download hgt data
>> that I then use to build DEM maps with mkgmap. For a long time, SRTM1
>> files (and also VFP1) have all been ~24.7 MB in size, but lately (I
>> don't remember since when) SRTM1 are also served as 12.4 MB files.
>> phyghtmap is able to generate contour lines from those small files, as
>> they seem to contain the same information but with a different
>> compression ratio, but mkgmap fails to read them, and report them as
>> missing. Would it be possible to get support for such files in mkgmap?
>> _______________________________________________
>> mkgmap-dev mailing list
>> mkgmap-dev at lists.mkgmap.org.uk
>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
>> _______________________________________________

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