[GRASSLIST:4491] Re: hgt to bil (SRTM)

[Markus Neteler]

On Wed, May 17, 2006 at 11:50:51AM +0200, ivan marchesini wrote:
> Dear Users,
> I'm trying to understand how to create the hdr file for the .bil srtm
> dem I downloaded....
> I have found too much different information...

In fact, there are many wrong documents in the Web.
Even the USGS docs were silently (!) fixed in December 2003.

> so I try with you....:
> if I have a N11E044.hgt file I have to rename the file to  N11E044.bil
> and then to create a N44E011.hdr file...

- SRTM filename coordinates are said to be the *center* of the LL pixel.
       N51E10 -> lower left cell center
-  BIL uses *center* of the UL (!) pixel:
      http://downloads.esri.com/support/whitepapers/other_/eximgav.pdf
  
-  GDAL uses *corners* of pixels for its coordinates (?)

[...]
Please have a look at
 http://mpa.itc.it/rs/srtm/index.html

where you can grab ready-to-use scripts:

srtm_generate_hdr.sh: general shell script to make GeoTIFF from original 
  SRTM90 files. Requires GDAL tools to be 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). 

Even the NASA is using it :-)
http://xserve.flids.com/pipermail/geotiff/2004-August/000052.html

Hope this helps

 Markus