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 alayer=string [atype=string[,string,...]] binput=name blayer=string [btype=string[,string,...]] 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
- Name of input vector map (A)
- alayer=string
- Layer number (vector map A)
- A single vector map can be connected to multiple database tables. This number determines which table to use. Layer name for direct OGR access.
- Default: 1
- atype=string[,string,...]
- Feature type (vector map A)
- Feature type
- Options: point,line,boundary,centroid,area
- Default: point,line,boundary,centroid,area
- binput=name
- Name of input vector map
- Name of input vector map (B)
- blayer=string
- Layer number (vector map B)
- A single vector map can be connected to multiple database tables. This number determines which table to use. Layer name for direct OGR access.
- Default: 1
- btype=string[,string,...]
- Feature type (vector map B)
- Feature type
- Options: point,line,boundary,centroid,area
- Default: point,line,boundary,centroid,area
- 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 forest fire points from larger fire vector map:
v.select ainput=fire binput=forest output=forest_fire operator=overlap
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
GRASS SQL interface
AUTHORS
Radim Blazek
Updated by Martin Landa, CTU in Prague, Czech Republic (GEOS support)
Last changed: $Date: 2010-11-07 09:34:38 -0800 (Sun, 07 Nov 2010) $
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