[GRASSLIST:3333] Re: SRTM data are not truly projected?

[Markus Neteler]

On Wed, Apr 28, 2004 at 05:38:15PM +0200, tatel at euskalnet.net wrote:
> Hi all,
> 
> I'd read this on SRTM_Topo.txt from srttm download site
> 
> ############# Quoating ###################################
> This sampling scheme is sometimes called a "geographic projection", but of
> course it is not actually a projection in the mapping sense. It does not
> possess any of the characteristics usually present in true map projections,
> for example it is not conformal, so that if it is displayed as an image
> geographic features will be distorted.
> ###########################################################
> 
> Does this mean I need to rectify SRTM data in order to make coincident
> with a MrSID image?

You may fetch the SRTM import script here:

http://mpa.itc.it/rs/srtm/
* 'srtm_generate_hdr.sh': general shell script to make GeoTIFF from 
      original SRTM90 files. Requires GDAL tools installed.

* 'r.in.srtm': GRASS script to import original SRTM files. 
    Requires above script to be installed in PATH. Fixes the INTEGER 
    encoding, applies color table. To use in Lat/Long LOCATIONS (WGS84, 
    to be precise EGM96).

Hope this helps,

 Markus

PS: It seems that you have to reproject to non-LatLong before
    using r.fillnulls.