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NAME

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

KEYWORDS

vector, geometry, spatial query

SYNOPSIS

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

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
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog

Parameters:

ainput=name [required]
Name of input vector map
Input vector map from which to select features (A)
alayer=string
Layer number (vector map A)
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
Default: 1
atype=string[,string,...]
Feature type (vector map A)
Input feature type
Options: point, line, boundary, centroid, area
Default: point,line,area
binput=name [required]
Name of input vector map
Query vector map (B)
blayer=string
Layer number (vector map B)
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
Default: 1
btype=string[,string,...]
Feature type (vector map B)
Input feature type
Options: point, line, boundary, centroid, area
Default: point,line,area
output=name [required]
Name for output vector map
operator=string [required]
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

Table of contents

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 (point in polygon test):
v.select ainput=firestations binput=urbanarea output=urban_firestations \
         operator=overlap
Extract railroad lines from zip code map overlapping with the urban area (line in polygon test):
v.select ainput=railroads binput=urbanarea \
         output=railroads_in_urbanarea operator=overlap
Extract those areas from zip code map which overlap with railroads (polygon on line test):
# first add a tiny buffer around railroad lines:
v.buffer input=railroads output=railroads_buf20m \
  distance=20

v.select ainput=zipcodes_wake binput=railroads_buf20m \
  output=zipcodes_wake_railroads operator=overlap

TODO

Processing areas with GEOS is currently incredibly slow. Significant speed-up is desired.

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: 2014-09-24 17:43:34 +0200 (st, 24 9 2014) $


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