This program may be especially useful when sampling for cross validation of interpolations whose output is a raster map.
When NULL values are encountered for a cell, zero value is used instead. In these cases, more acurrate results may be obtained by using the default nearest neighbor comparisons.
This program may not work properly with lat-long data when the -bc flags are used.
When interpolation is done (i.e., the -bc flags are used), values are assumed to be located at the centroid of grid cells. Therefore, current resolution settings are important.
#generate random points: v.random output=random n=100 #add table with one column: v.db.addtable random col="el10 double" #transfer elevations at random points into table: v.what.rast rast=elevation.10m vect=random col=el10 #verify: v.db.select random #generate sampling from other elevation map: v.sample in=random col=el10 rast=elevation.dem out=elev_sample #verify: v.db.select elev_sample #univariate statistics of differences between elevation maps: v.univar elev_sample col=diff type=point
Updated for GRASS 5.0 by Eric G. Miller
Updated for GRASS 5.7 by Radim Blazek
Last changed: $Date$