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? And barring that, any suggestions for an alternative site of bathymetry I can patch into my Europe map?
Thanks
Michael
Michael Barton, Professor of Anthropology
Director of Graduate Studies
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University
phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton
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
Thanks for the useful hints Maciej.
I tried to unzip (as the docs say) and found that they are not zipped. Then
I tried to follow the Russian-doll-like descriptions of 'these are formatted
like the previous releases' in the brief docs back to USGS EROS where I
could not find (yet) a decent description of the format.
I'll try your suggestions.
Michael
On 10/13/07 8:27 AM, "Maciej Sieczka" <tutey@o2.pl> wrote:
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] Raster drivers — GDAL documentation
Maciek
__________________________________________
Michael Barton, Professor of Anthropology
Director of Graduate Studies
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University
phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton