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

From Carlos Dávila carlos at alternativaslibres.org on Mon Oct 5 15:01:12 BST 2020 

Thanks!!

El 5/10/20 a las 8:13, Gerd Petermann escribió:
> Hi Carlos,
>
> sorry, no idea what went wrong with the communication. I've now committed the patch with r4586.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Carlos Dávila <carlos at alternativaslibres.org>
> Gesendet: Mittwoch, 24. Juni 2020 19:12
> An: Development list for mkgmap
> Betreff: [mkgmap-dev] Fwd: Re:  "Small" SRTM1 files and DEM maps
>
> 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
>>>>>> _______________________________________________
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