Thanks for all the explanations. Now I know better. Below [1], I tried to bring all relevant snippets together. Wouldn't it make sense to add some of these details to g.region.html, or so?
Hermann [1] Glynn and Hamish gave these helpful explanations: > to sum up: > > * r.in.gdal differs from most raster modules in that it imports > the entire map and ignores the current region. > > * gdal_translate can be used to crop out an area of interest > before import with its -projwin or -srcwin options. > > * after import any subsequent raster module will respect the > region settings, so in effect crop to the current region. The > most basic example of this is: "r.mapcalc "cropped = imported". > > Hermann: >> By the way: is there a convenient overview of raster >> modules that do NOT respect the current region? > > no, but the general theme is that raster modules which import > pre-existing datasets (r.in.*) preserve that data arrays; while > modules which create new raster maps (r.* including v.to.rast, > r.in.poly, r.in.xyz, and r.proj) will respect the region. > > and then of course there will always be an exception or two to > the rule, but you can pretty much trust the above. > > > r.reclass doesn't read or write raster data, so the region doesn't > come into it. > > Similar issues apply to r.info, r.support, r.compress, r.null, > r.timestamp etc. > > The region only matters for modules which read or write raster data. > This includes most (but not all) r.* and i.* modules, as well as some > other modules (e.g. v.what.rast). > > In general: r.in.* ignore the region, and import rasters > cell-for-cell. r.resamp.* and r.proj ignore the region for reading but > honour it for writing. > > > A reclass map is just a reference to the base map and a list of > category mappings. It doesn't have a region of its own; e.g. if you > change the bounds of the base map via r.region, the bounds of the > reclass map will change to match. > _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
