
NAME
v.external - Creates a new pseudo-vector map as a link to an OGR-supported layer.
KEYWORDS
vector, external, ogr
SYNOPSIS
v.external
v.external help
v.external [-flb] dsn=string layer=name [output=name] [--overwrite] [--verbose] [--quiet]
Flags:
- -f
- List supported OGR formats and exit
- -l
- List available OGR layers in given data source and exit
- -b
- Do not build topology
- --overwrite
- Allow output files to overwrite existing files
- --verbose
- Verbose module output
- --quiet
- Quiet module output
Parameters:
- dsn=string
- Name of input OGR data source
- Examples:
ESRI Shapefile: directory containing a shapefile
MapInfo File: directory containing a mapinfo file
PostGIS database: PG:dbname=<database>
- layer=name
- Name of input OGR layer
- Examples:
ESRI Shapefile: shapefile name
MapInfo File: mapinfo file name
PostGIS database: table name
- output=name
- Name for output GRASS vector map
DESCRIPTION
v.external creates new vector as a link to external
OGR layer (read only).
OGR (Simple Features Library) is part of the
GDAL library, so you need to
install GDAL to use v.external and external OGR layers.
Supported OGR Vector Formats
Further available drivers such as UK .NTF, SDTS, TIGER, IHO S-57
(ENC), DGN, GML, AVCBin, REC, Memory, OGDI, and PostgreSQL depend on
the local installation (OGR library), for details see
OGR web site.
EXAMPLES
SHAPE files
v.external dsn=/home/user/shape_data layer=test_shape output=grass_map
MapInfo files
v.external dsn=./ layer=mapinfo_test output=grass_map
SDTS files (you have to select the CATD file)
v.external dsn=CITXCATD.DDF output=cities
TIGER files
v.external dsn=input/2000/56015/ layer=CompleteChain,PIP output=t56015_all
PostGIS layers (area example)
v.external dsn="PG:host=localhost user=postgres dbname=postgis" layer=polymap \
output=polygons
NOTES
The simple feature data model used by OGR is very different from the
topological format used by GRASS. Instead of true topology, so called
'pseudo topology' is created for data linked by v.external. User
should learn the difference between those to formats, because some
modules working correctly with GRASS native data, can produce wrong
results with input layers created by v.external.
See v.db.connect for an example of
maintaining attributes in external DBMS in also writeable mode.
REFERENCES
OGR vector library
OGR vector library C API
documentation
SEE ALSO
v.clean,
v.db.connect,
v.in.db,
v.in.ogr,
v.out.ogr
AUTHOR
Radim Blazek, ITC-Irst, Trento, Italy
Last changed: $Date: 2009-07-12 02:48:05 -0700 (Sun, 12 Jul 2009) $
Main index - vector index - Full index
© 2003-2011 GRASS Development Team