[CC'd to grass-dev.]
beakins wrote:
One question that I have: "Is there another file format for the ETOPO1 grids
that would be of more use to the GRASS community than netcdf?" We could host
something such as geotiffs of the grids, which we can create easily, but I'm
not a GRASS user so don't know what grid/raster file format would be easiest
to import into GRASS. I've also never used QGIS.Any ideas or suggestions would be much appreciated.
GRASS' preferred raster format is anything which GDAL supports, and
for which GetGeoTransform() succeeds, with the adfTransform array
satisfying the constraints:
adfTransform[1] > 0
adfTransform[2] == 0
adfTransform[4] == 0
adfTransform[5] < 0
[Currently, r.in.gdal/r.external don't bother to check
adfTransform[1]; if it's negative, GRASS may import it okay, but then
refuse to read it.]
IOW, north-to-south, west-to-east, no rotation or shear. If the data
uses a different orientation, GDAL needs to be able to transform it
itself. It isn't a major problem if the georeferencing data isn't
readily available, but a different orientation is (at present).
Ultimately, we could make some changes to support flipped (but not
rotated) rasters, but the format would ideally need to be such that
there isn't a penalty for reading data north-to-south, i.e. any
south-to-north data would need to be in a format which supports
non-sequential access (seeking).
--
Glynn Clements <glynn@gclements.plus.com>