GRASS GIS manual: v.select

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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] [--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; Default: overlap; overlap: features partially or completely overlap

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.

AUTHORS

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

Last changed: $Date: 2012-12-10 02:28:57 -0800 (Mon, 10 Dec 2012) $

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