NAME¶

v.overlay - Overlays two vector maps.

KEYWORDS¶

vector, geometry

SYNOPSIS¶

v.overlay v.overlay help v.overlay [-t] ainput=name [atype=string[, string,...]] [alayer=integer] binput=name [btype=string[, string,...]] [blayer=integer] output=name [operator=string] [ olayer=integer[,integer,...]] [-- overwrite] [--verbose] [--quiet]

Flags:¶

-t

 

Do not create attribute table

--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: line,area

 

Default: 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: area

 

Default: 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 features written to output vector map

 

Feature is written to output if the result of operation 'ainput operator binput' is true. Input feature is considered to be true, if category of given layer is defined.

 

Options: and,or,not,xor

 

Default: or

 

and: also known as 'intersection' in GIS

 

or: also known as 'union' in GIS (only for atype=area)

 

not: features from ainput not overlayed by features from binput

 

xor: features from either ainput or binput but not those from ainput overlayed by binput (only for atype=area)

olayer=integer[,integer,...]

 

Output layer for new category, ainput and binput

 

If 0 or not given, the category is not written

 

Default: 1,0,0

DESCRIPTION¶

v.overlay allows the user to overlay two vector area maps. The resulting output map has a merged attribute-table. The origin column-names have a prefix ( a_ and b_) which results from the ainput- and binput-map.

NOTES¶

Currently only areas are supported for the operators or and xor! See also v.select. The operator defines what kind of operation will be done. Features are written to output, if the result of an operation 'ainput operator binput' is true. Attributes of the tables from ainput and binput are joined into a new table linked to the output maps new cat-column.

EXAMPLE POLYGON TO POLYGON UNION¶

v.overlay ainput=lake binput=province output=lakeXprovince operator=or

EXAMPLE LINE TO POLYGON CLIPPING¶

Using the North Carolina sample dataset, we clip the roads map to the area of city of Raleigh: g.region vect=zipcodes_wake # extract Raleigh city v.extract in=zipcodes_wake out=raleigh \
where="ZIPNAME = 'RALEIGH'" # clip road network to city polygon: v.overlay ainput=roadsmajor atype=line binput=raleigh \
out=roadsmajor_raleigh operator=and | v.overlay: Line to polygon clipping

SEE ALSO¶

v.db.connect, v.select, g.copy

AUTHORS¶

Radim Blazek, ITC-Irst, Trento, Italy Last changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $ Full index © 2003-2011 GRASS Development Team