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] [-- 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

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 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 GRASS SQL interface

AUTHORS¶

Radim Blazek Updated by Martin Landa, CTU in Prague, Czech Republic (GEOS support) Last changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $ Full index © 2003-2011 GRASS Development Team