NAME
v.overlay - Overlay 2 vector maps.
SYNOPSIS
v.overlay
v.overlay help
v.overlay [-t] ainput=string [atype=string[,string,...]] [afield=integer] binput=string [btype=string[,string,...]] [bfield=integer] output=string [operator=string] [ofield=integer[,integer,...]]
Flags:
- -t
- Do not create attribute table.
Parameters:
- ainput=string
- Name of input vector
- atype=string
- Select type: point, line, boundary, centroid or area
- Options: line,area
- Default: area
- afield=integer
- Field value
- Default: 1
- binput=string
- Name of input vector
- btype=string
- Select type: point, line, boundary, centroid or area
- Options: area
- Default: area
- bfield=integer
- Field value
- Default: 1
- output=string
- Name of output vector
- operator=string
- Operator defines features written to output vector. 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 field is defined.
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)
- Options: and,or,not,xor
- Default: or
- ofield=integer
- Output field for new category, ainput and binput. If 0 or not given, the category is not written.
- Default: 1,2,3
DESCRIPTION
v.overlay allows the user to overlay to vector area maps.
There are 3 links attached to features in output map,
- field 1: link to the new table, new table has 3 columns
- cat - key column linking rows to features
- cata - category of afield from ainput
- catb - category of bfield from binput
- field 2: category of afield from ainput
- field 3: category of bfield from binput
NOTES
Currently only areas are supported!
Joining attribute tables from ainput and binput into a new table linked to the
output map is not implemented yet.
To query categories from ainput and/or binput it is necessary to link the
related tables to fields with v.db.connect.
v.db.connect map=outputmap table=ainput.dbf
field=2
v.db.connect map=outputmap table=binput.dbf
field=3
Attention: Removing the output map will also delete all tables linked to
it! Therefore it is advisable to copy tables from ainput and binput first and
connect the copied tables to the output map.
EXAMPLE
v.overlay ainput=lake binput=province output=lakeXprovince
SEE ALSO
v.db.connect
g.copy
AUTHORS
Radim Blazek, ITC-Irst, Trento, Italy
Last changed: $Date: 2004/09/17 15:15:50 $
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