#789: g.region option to expand the computational region of about "some" pixels? ---------------------------------------------------+------------------------ Reporter: nikos | Owner: [email protected] Type: enhancement | Status: new Priority: normal | Milestone: 7.0.0 Component: default | Version: unspecified Keywords: g.region, expand computational region | Platform: Unspecified Cpu: Unspecified | ---------------------------------------------------+------------------------ Let's accept that we have a set of point (vector) maps and we need to update one of their attributes by querying a raster map. We would use v.what.rast of course to get the job done.
Now, in order to save time and system resources, we would like to match the active region over the point map since we care about this area of the raster map (from which v.what.rast will grab the values and feed some column in the point map). We could execute for example: "g.region res=ResOfRaster vect=PointMap -pa" Matching the region over a point map is the problem! The points at the borders (happens quite often to me when the resolution of the raster map is low and so does the resolution of the region successively) are not taken into account. To overcome the problem I had to find a way to "grow the region" so the region matching is "v.what.rast safe" :-). OK, in my case it was easy as the points where actually centroids extracted from a vector grid map. So matching the region to the original vector grid map did it. But what if it's not the case to have a vector, enough larger than the point map, to perform a "v.what.rast safe" region matching? (a) anybody else facing this problem? Herewith I would like to suggest the implementation of a new option for g.region, a "v.what.rast-safe" option :-p (b) is it difficult to build in a flag (let's say -x which will stand for eXpand) to "grow" the (2D) region in both, vertical and horizontal manner of about 1(or more?) pixel(s) (where pixel size here is meant to be the resolution of the 2D raster map to be queried)? I imagine something that would use r.mapcalc (or r.mask), r.grow and g.region itself? Thanks for reading, Nikos -- Ticket URL: <http://trac.osgeo.org/grass/ticket/789> GRASS GIS <http://grass.osgeo.org>
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