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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) $

       Full index

       © 2003-2013 GRASS Development Team



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