[Gdal-dev] Re: GDAL SRTM hgt code

[Rick Niles]

Since SRTM hgt-files is the best public available terrain data around 
(that I know of..), it seems like it's worth it to have a specific 
front-end to handle it directly via GDALOpen().  I can see why some 
would argue that's just a special case of a raw 2-byte file, but I don't 
think it would be ugly to have a specific filter to handle this 
extremely popular data.  There's 3-second and 1-second SRTM data and I'm 
not sure you can auto-detect which is which.

What do you think?

Rick Niles.


WolfgangZ wrote:
> list67 at netscape.net schrieb:
>> Has anyone added code to GDAL so that a SRTM (1 or 3 arcsecond) hgt 
>> file can be passed to GDALOpen(...) for use?
>>
>> I did some searching and noticed that there are some format 
>> conversion workarounds for using the SRTM files with GDAL, but I 
>> didn't find any info about wether or not a more direct open 
>> capability had been implemented?
>>
>> Thank you.
>>
>>    Mike
>
> hi Mike,
>
> you can have a look at the grass r.in.srtm script. It basically unzips 
> and renames the file to .bil and furthermore you need to create a 
> textfile with the same file name and the fiel ending .hdr with the 
> following content:
> For 3arcsec data:
>     BYTEORDER M
>     LAYOUT BIL
>     NROWS 1201
>     NCOLS 1201
>     NBANDS 1
>     NBITS 16
>     BANDROWBYTES 2402
>     TOTALROWBYTES 2402
>     BANDGAPBYTES 0
>     NODATA -32768
>     ULXMAP $ULXMAP
>     ULYMAP $ULYMAP
>     XDIM 0.000833333333333
>     YDIM 0.000833333333333
>
> of for 1arcsec data:
>     BYTEORDER M
>     LAYOUT BIL
>     NROWS 3601
>     NCOLS 3601
>     NBANDS 1
>     NBITS 16
>     BANDROWBYTES 7202
>     TOTALROWBYTES 7202
>     BANDGAPBYTES 0
>     NODATA -32768
>     ULXMAP $ULXMAP
>     ULYMAP $ULYMAP
>     XDIM 0.000277777777777778
>     YDIM 0.000277777777777778
>
> You need to replace $ULXMAP and $ULYMAP with the upper left 
> coordinates of that tile. As s_srs you can use EPSG:4326.
>
> Greetings
> Wolfgang
>
>
> _______________________________________________
> Gdal-dev mailing list
> Gdal-dev at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/gdal-dev