NAMEv.select - Selects features from vector map (A) by features from other vector map (B).
KEYWORDSvector, spatial query
SYNOPSISv.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
DESCRIPTIONv.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
NOTESOnly 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.
EXAMPLESExtract forest fire points from larger fire vector map: v.select ainput=fire binput=forest output=forest_fire operator=overlap Extract Italian rivers from VMAP0 watercourses map: v.select ainput=watrcrsl_eurnasia_wgs84 binput=italy_area \ output=watrcrsl_italy operator=overlap
TODOProcessing areas with GEOS is currently incredibly slow. Significant speed-up is required.
SEE ALSOv.category, v.overlay GRASS SQL interface
AUTHORSRadim Blazek Updated by Martin Landa, CTU in Prague, Czech Republic (GEOS support) Last changed: $Date: 2010-11-07 18:37:50 +0100 (Sun, 07 Nov 2010) $ Full index (C) 2003-2010 GRASS Development Team V.SELECT(1)