Provided by: grass-doc_6.4.3-3_all
v.select - Selects features from vector map (A) by features from other vector map (B).
vector, spatial query
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
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
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.
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
Processing areas with GEOS is currently incredibly slow. Significant speed-up is required.
v.category, v.overlay, v.extract GRASS SQL interface
Radim Blazek GEOS support by Martin Landa, Czech Technical University in Prague, Czech Republic Last changed: $Date: 2012-12-10 02:32:07 -0800 (Mon, 10 Dec 2012) $ Full index © 2003-2013 GRASS Development Team