NAME

       v.select  - Selects features from vector map (A) by features from other vector map (B).

KEYWORDS

       vector, spatial query

SYNOPSIS

       v.select
       v.select help
       v.select  [-tcr]  ainput=name  [atype=string[,string,...]]   [alayer=integer]  binput=name
       [btype=string[,string,...]]       [blayer=integer]      output=name      [operator=string]
       [relate=string]   [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -t
           Do not create attribute table

       -c
           Do not skip features without category

       -r
           Reverse selection

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       ainput=name
           Name of input vector map (A)

       atype=string[,string,...]
           Feature type (vector map A)
           Feature type
           Options: point,line,boundary,centroid,area
           Default: point,line,boundary,centroid,area

       alayer=integer
           Layer number (vector map A)
           A  single  vector  map  can  be  connected  to  multiple  database tables. This number
           determines which table to use.
           Default: 1

       binput=name
           Name of input vector map (B)

       btype=string[,string,...]
           Feature type (vector map B)
           Feature type
           Options: point,line,boundary,centroid,area
           Default: point,line,boundary,centroid,area

       blayer=integer
           Layer number (vector map B)
           A single vector map  can  be  connected  to  multiple  database  tables.  This  number
           determines which table to use.
           Default: 1

       output=name
           Name for output vector map

       operator=string
           Operator defines required relation between features
           A  feature is written to output if the result of operation 'ainput operator binput' is
           true. An input feature is considered to  be  true,  if  category  of  given  layer  is
           defined.
           Options:
           overlap,equals,disjoint,intersects,touches,crosses,within,contains,overlaps,relate
           Default: overlap
           overlap: features partially or completely overlap
           equals: features are spatially equals (using GEOS)
           disjoint: features do not spatially intersect (using GEOS)
           intersects: features spatially intersect (using GEOS)
           touches: features spatially touches (using GEOS)
           crosses: features spatially crosses (using GEOS)
           within: feature A is completely inside feature B (using GEOS)
           contains: feature B is completely inside feature A (using GEOS)
           overlaps: features spatially overlap (using GEOS)
           relate: feature A is spatially related to feature B  (using  GEOS,  requires  'relate'
           option)

       relate=string
           Intersection Matrix Pattern used for 'relate' operator

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
        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, v.extract

       GRASS SQL interface

AUTHORS

       Radim Blazek
       GEOS support by Martin Landa, Czech Technical University in Prague, Czech Republic

       Last changed: $Date: 2012-12-10 02:32:07 -0800 (Mon, 10 Dec 2012) $

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