Re: Re: [gdal-dev] Aster tif files to hgt

Jaromír Mikeš mira.mikes at
Mon Nov 7 18:09:44 EST 2011

> Od: Hermann Peifer <peifer at>

> >> Od: Jaromír Mikeš<mira.mikes at>

> > Now I need resample files from 1 arc-second (30m) resolution to 3 arc-second
> (90m).
> > Can this be done with gdal?

> Did you try an Internet search with "gdal resample" as search words?

Hello Hermann,

I found this example while ago:
(section "Hill shading")

Now I trying do something like this in my perl script:
	`gdalwarp -of GTiff -srcnodata 32767 -t_srs "+proj=merc +ellps=sphere +R=6378137 +a=6378137 +units=m"-rcs -order 3 -tr 90 90 -multi ASTGTM2_${tile}_dem.tif ${tile}.tif` ;

	`gdal_translate -of SRTMHGT ${tile}.tif ${tile}.hgt` ;

I am getting errors on creating hgt files:
Warning 1: The source projection coordinate system is PROJCS["unnamed",GEOGCS["unnamed ellipse",DATUM["unknown",SPHEROID["unnamed",6378137,0]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Mercator_1SP"],PARAMETER["central_meridian",0],PARAMETER["scale_factor",1],PARAMETER["false_easting",0],PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]]]. Only WGS 84 is supported.
The SRTMHGT driver will generate a file as if the source was WGS 84 projection coordinate system.
Warning 1: The corner coordinates of the source are not properly aligned on plain latitude/longitude boundaries.
ERROR 1: Image dimensions should be 1201x1201 or 3601x3601.

Looks like problem is in -t_srs option, gdalwarp is not work if I remove this option totally.

I tried also +proj=WGS84, but it wasn't recognized as right option.

Also this "+proj=utm +datum=WGS84" I tried with error:
ERROR 1: Too many points (441 out of 441) failed to transform,
unable to compute output bounds.

Any hint where I can find more info about -t_srs options?
BTW I am doing map for southern hemisphere, not shure if this matter. 



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