NAME

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

KEYWORDS

       vector, raster, attribute table

SYNOPSIS

       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

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 a column of the
       attribute table connected to the 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:

       # create new random vector points map
       v.random pnts n=100
       # add new table, link to map
       v.db.addtable pnts col="heights double precision"
       # query raster map and upload values to vector table into specified column
       g.region rast=elevation -p
       v.what.rast vect=pnts raster=elevation column=heights
       # verify new attribute table:
       v.db.select pnts
       # verify statistics of uploaded values:
       v.univar map=pnts column=heights 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: 2012-02-08 13:39:58 -0800 (Wed, 08 Feb 2012) $

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                  v.what.rast(1grass)