DESCRIPTION
v.select allows the user to select features from a vector
map by features from another one.
Supported operators (without GEOS):
- overlap - features partially or completely overlap
Supported operators (with GEOS):
- equals - features are spatially equals
- disjoint - features do not spatially intersect
- intersects - features spatially intersect
- touches - features spatially touches
- crosses - features spatially crosses
- within - feature A is completely inside feature B
- contains - feature B is completely inside feature A
- overlaps - features spatially overlap
- relate - feature A is spatially related to feature B
NOTES
Only features with category numbers will be considered. If required
the v.category module can be
used to add them. Typically boundaries do not need to be given a
category number, as an area's attributes are inherited from the
centroid. Typically points, lines, and centroids will always want to
have a cat number. E.g. take a road which separates two farms. It is
ambiguous as to which farm an attribute that is attached to the road
belongs to. The boundary only needs a cat number if it will hold its
own attributes, such as road name or pavement form. A centroid in each
paddock holds the information with respect to ownership, area, etc.
EXAMPLES
Extract fire stations (points) from urban area map (polygon) - North Carolina
data set:
v.select ainput=firestations binput=urbanarea output=urban_firestations \
operator=overlap
v.select ainput=watrcrsl_eurnasia_wgs84 binput=italy_area \
output=watrcrsl_italy operator=overlap
TODO
Processing areas with GEOS is currently incredibly slow. Significant
speed-up is required.
SEE ALSO
v.category,
v.overlay,
v.extract
GRASS SQL interface
AUTHORS
Radim Blazek
GEOS support by Martin Landa, Czech Technical University in Prague, Czech Republic
Last changed: $Date$