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] [ 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

DESCRIPTION¶

v.select allows the user to select features from a vector map by features from another one. Supported operators (without GEOS): Supported operators (with GEOS):

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.

SEE ALSO¶

v.category, v.overlay, v.extract GRASS SQL interface

AUTHORS¶

Radim Blazek GEOS support by Martin Landa, Czech Technical University in Prague, Czech Republic Last changed: $Date: 2012-12-10 11:32:07 +0100 (Mon, 10 Dec 2012) $ Full index © 2003-2014 GRASS Development Team