Raphael wrote: > > i have imported the etopo dem (geotifff) into grass. > > It appears to be in XY and i would like to convert > > these to lat longs.
MarkusN: > I looked at > http://grass.osgeo.org/wiki/Global_datasets#ETOPO_.28DEM.29 > > and was surprised to see the XY thing there for ETOPO1. there are two versions available. note the ETOPO-1 wiki section starts with "The cell registered version can be loaded directly into a lat/lon region." That one will load directly into the lat/lon region; I've bolded that text now. but the NOAA site states "The grid-registered is the authoritative registration. The cell-registered is derived from the grid-registered, and the conversion produces slightly flattened relief. More about grid registration: http://www.ngdc.noaa.gov/mgg/global/gridregistration.html " I think the "import into XY, crop outer edge & recenter" before converting the XY location into a lat/lon loc'n hack was written before the 'r.in.gdal -l' flag + fix with r.region came to be (perhaps because of?), and since these datasets need r.in.bin you'd need to compose a gdal .vrt file describing the byte order etc to use r.in.gdal? > But in any case the ETOPO2 will be better (see wiki for an > article how to import it). yes for ease of import, but not so much for modernity. "Historic ETOPO2v2 and ETOPO5 global relief grids are deprecated but still available." for ETOPO2 the authoritative registration was cell-centered, which is the same as GRASS uses, so everything lines up and it's a lot easier. Hamish _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user