[GRASS-user] srtm plus format and European bathymetry

[Maciej Sieczka]

Michael Barton wrote:
> Ultimately, I'm trying to locate bathymetry off the coast of Europe to
> create a DEM of Pleistocene Europe during times of low sea level (i.e.,
> -300m). 
> 
> Following the FreeGIS.org link off the GRASS download data page, I found a
> site with "STRM30 plus" that combine 1km SRTM with bathymetry
> <ftp://topex.ucsd.edu/pub/srtm30_plus/data>. This seems just what I need.
> However, I can't figure out the format or how to import it into GRASS. The
> files show up like " w020n90.Bathmetry.srtm". I've tried r.in.gdal and
> r.in.strm to no avail. I thought maybe the files were compressed and tried
> to uncompress them without luck.
> 
> Can anyone suggest what to do with these files? 

Michael,

ftp://topex.ucsd.edu/pub/srtm30_plus/README.V2.0.txt:

<snip>
DATA FORMATS
Data are provided as binary integers in exactly the same
format as SRTM30.  The files must be uncompressed with gzip
and are 16-bit big endian byte order.
</snip>

Other than they don't seem gzipped actually, the information
looks correct. These are 16 bit signed integer binary grids.

You can use r.in.bin, or r.in.gdal if you create appropriate
header files (see r.in.srtm script for inspiration; note it
cannot work with 30" SRTM data as it is now - currently it
supports only 3" and 1" SRTM tiles). In the presence of
properly formatted *.hdr GDAL supports such binary grids
with "ESRI .hdr Labelled" driver [1]. In
ftp://topex.ucsd.edu/pub/srtm30_plus/ermapper_headers there
are ERmapper header files, which I suppose can be used to
prepare their GDAL-understandable version.

[1] http://www.gdal.org/frmt_various.html#EHdr

Maciek