
NAME
v.select - Selects features from vector map (A) by features from other vector map (B).
KEYWORDS
vector, query
SYNOPSIS
v.select
v.select help
v.select [-tr] 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
- -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
by features from another one.
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 forest fire points from larger fire map:
v.select ainput=fire binput=forest output=forest_fire
Extract Italian rivers from VMAP0 watercourses map:
v.select ainput=watrcrsl_eurnasia_wgs84 binput=italy_area \
output=watrcrsl_italy operator=overlap
SEE ALSO
v.category,
v.overlay,
GRASS SQL interface
AUTHORS
Radim Blazek
Last changed: $Date: 2008-12-13 18:43:05 +0100 (Sat, 13 Dec 2008) $
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