v.select(1)

NAME
v.select

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 forest fire points from larger fire vector map:
v.select ainput=fire binput=forest output=forest_fire operator=overlap
Extract Italian rivers from VMAP0 watercourses map:
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

GRASS SQL interface

AUTHORS
Radim Blazek
Updated by Martin Landa, CTU in Prague, Czech Republic (GEOS support)

Last changed: $Date: 2010-11-07 18:37:50 +0100 (Sun, 07 Nov 2010) $

Full index

© 2003-2010 GRASS Development Team