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: $Date$