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

Wed Jun 24 18:12:00 BST 2020

Hi Gerd

I replied to your patch a couple of months ago, but I have now realized 
it didn't arrive to the list (it seems I used and old address). I was 
surprised you didn't say anything, but didn't want to bother...

I used your binary for my test. Today I have tried to apply your patch, 
but it seems to be generated against a different version of files in trunk.

-------- Mensaje reenviado --------
Asunto: 	Re: [mkgmap-dev] "Small" SRTM1 files and DEM maps
Fecha: 	Tue, 21 Apr 2020 17:38:19 +0200
De: 	Carlos Dávila <cdavilam at orangecorreo.es>
Para: 	mkgmap-dev at lists.mkgmap.org.uk

Hi Gerd
I have tested it in an area of 4x10 degrees, in the North of China, and 
it worked fine.

El 21/4/20 a las 14:40, Gerd Petermann escribió:
> Hi Carlos,
>
> please try the attached patch or this binary based on r4483:
> http://files.mkgmap.org.uk/download/468/mkgmap.jar
> I hope I found all the places that need to be changed. I've only 
> tested with a map around the point N50 E118.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag 
> von Carlos Dávila <carlos at alternativaslibres.org>
> Gesendet: Dienstag, 21. April 2020 11:27
> An: mkgmap-dev at lists.mkgmap.org.uk
> Betreff: Re: [mkgmap-dev] "Small" SRTM1 files and DEM maps
>
> Great new!! Thanks for your support
>
> El 21/4/20 a las 11:19, Gerd Petermann escribió:
>> Hi Carlos,
>>
>> yes, I see that the source code handles this format. I finally found
>> https://dds.cr.usgs.gov/srtm/version2_1/Documentation/MIL-PDF-89020B.pdf
>> I think "TABLE I. Matrix intervals for DTED Level 0."
>> shows how to interpret the data. It seems there are a few more 
>> variants...
>> For now I'll try to support also the 1801 * 3601 * 2 format
>>
>> Gerd
>>
>> ________________________________________
>> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag 
>> von Carlos Dávila <carlos at alternativaslibres.org>
>> Gesendet: Donnerstag, 16. April 2020 17:41
>> An: mkgmap-dev at lists.mkgmap.org.uk
>> Betreff: Re: [mkgmap-dev] "Small" SRTM1 files and DEM maps
>>
>> HI Gerd
>> I don't think conversion is wrong. If input geotiff file is 24MB, output
>> hgt file is 24 MB, if input tiff is 12MB, output hgt is 12MB
>> I use this command on Linux:
>> for i in *.tif ; do gdal_translate -strict -q -eco -of SRTMHGT $i
>> `basename $i tif`hgt ; done ; rm -f *.hgt.aux.xml
>> BTW, gdal is also able to deal with small SRTM files
>>
>> El 16/4/20 a las 11:31, Gerd Petermann escribió:
>>> 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
>>>>> _______________________________________________
>