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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 < 1000 and inhab >= 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 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: 2007-06-10 04:23:21 -0700 (Sun, 10 Jun 2007) $
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