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 22:39:58 +0100 (Wed, 08 Feb 2012) $
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