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man page of v.what.rast

v.what.rast: Uploads raster values at positions of vector points to the table.


v.what.rast - Uploads raster values at positions of vector points to the table.


vector, raster, attribute table


v.what.rast v.what.rast help v.what.rast vector=name raster=name [layer=integer] column=string [where=sql_query] [--verbose] [--quiet] Parameters: vector=name Name of input vector points map for which to edit attribute table raster=name Name of existing raster map to be queried layer=integer Layer number A single vector map can be connected to multiple database tables. This number determines which table to use. Default: 1 column=string Column name (will be updated by raster values) where=sql_query WHERE conditions of SQL statement without 'where' keyword Example: income = 10000
v.what.rast reads raster value for each point in the vector and updates col column in vector attribute table by this value. The column should be type number (integer, float, double, ... ). If more points have the same category, attribute value is set to NULL. If raster values is NULL, attribute value is set to NULL.
v.what.rast operates on the attribute table. To modify the vector geometry instead, use v.drape.


A) Reading values from raster map at position of vector points, writing these values into column of vector map: v.what.rast vect=pnts rast=elevation col=heights B) In case of a vector map without attached attribute table, first add a new attribute table. This table is then populated with values queried from the raster map: v.db.connect -p vectpoints # .. no table yet. # add new table, link to map: v.db.addtable vectpoints col="cat integer, myvalue integer, otherval double precision" # query raster map and upload values to vector table into specified column: v.what.rast vect=vectpoints rast=rastmap col=myvalue # verify new attribute table: v.db.select vectpoints # verify statistics of uploaded values: v.univar map=vectpoints col=myvalue type=point


v.db.addtable, v.db.select, v.drape, v.univar, v.rast.stats, v.what.vect


Radim Blazek Last changed: $Date: 2007-06-10 13:23:21 +0200 (Sun, 10 Jun 2007) $ Full index (C) 2003-2010 GRASS Development Team V.WHAT.RAST(1)

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