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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):

Supported operators (with GEOS):

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) falling into urban area (polygon) - North Carolina data set:
v.select ainput=firestations binput=urbanarea output=urban_firestations \
         operator=overlap
Extract river lines from Eurasian rivers map overlapping with the Italian political area:
v.select ainput=rivers_eurasia binput=italy_area \
         output=rivers_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: 2014-08-19 09:28:57 -0700 (Tue, 19 Aug 2014) $


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