DESCRIPTION

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.

NOTES

v.what.rast operates on the attribute table. To modify the vector geometry instead, use v.drape.

EXAMPLES

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

SEE ALSO

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

AUTHOR

Radim Blazek

Last changed: $Date$