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v.external(1grass) | Grass User's Manual | v.external(1grass) |
NAME¶
v.external - Creates a new pseudo-vector map as a link to an OGR-supported layer or a PostGIS feature table.KEYWORDS¶
vector, import, external, OGR, PostGISSYNOPSIS¶
v.externalv.external --help
v.external [-ofltb] input=string [layer=name] [output=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:¶
- -o
-
Override projection check (use current location’s projection)
Assume that the dataset has the same projection as the current location - -f
-
List supported formats and exit - -l
-
List available layers in data source and exit - -t
-
List available layers including feature type in data source and exit
Format: layer name,type,projection check,geometry - -b
-
Do not build topology
Advantageous when handling a large number of points - --overwrite
-
Allow output files to overwrite existing files - --help
-
Print usage summary - --verbose
-
Verbose module output - --quiet
-
Quiet module output - --ui
-
Force launching GUI dialog
Parameters:¶
- input=string [required]
-
Name of input OGR or PostGIS data source
Examples:
ESRI Shapefile: directory containing a shapefile
MapInfo File: directory containing a mapinfo file
PostGIS database: connection string, eg. ’PG:dbname=db user=grass’ - layer=name
-
Name of OGR layer or PostGIS feature table to be linked
Examples:
ESRI Shapefile: shapefile name
MapInfo File: mapinfo file name
PostGIS database: table name - output=name
-
Name for output GRASS vector map (default: input layer)
DESCRIPTION¶
v.external creates new vector map as a link to external OGR layer or PostGIS feature table. OGR (Simple Features Library) is part of the GDAL library, so you need to install GDAL to use v.external for external OGR layers. Note that a PostGIS feature table can be linked also using built-in GRASS-PostGIS data driver (requires GRASS to be built with PostgreSQL support).Supported OGR vector formats¶
To list supported OGR formats, typev.external -fFor details see OGR web site.
EXAMPLES¶
ESRI Shapefile¶
Assuming that ’test_shape.shp’ is located in directory ’/home/user/shape_data’.v.external input=/home/user/shape_data layer=test_shape output=grass_map
MapInfo files¶
v.external input=./ layer=mapinfo_test output=grass_map
SDTS files¶
Note: you have to select the CATD filev.external input=CITXCATD.DDF output=cities
TIGER files¶
v.external input=input/2000/56015/ layer=CompleteChain,PIP output=t56015_all
PostGIS layers¶
PostGIS links are by default created by built-in PostGIS support, ie. using GRASS-PostGIS data driver. If the environment variable GRASS_VECTOR_OGR exists, or GRASS is compiled without PostgreSQL support then GRASS will use OGR-PostgreSQL driver for creating a link.v.external input="PG:host=localhost user=postgres dbname=postgis" layer=polymap
NOTES¶
The simple feature data model used by OGR (or PostGIS) 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 two formats, because some modules working correctly with GRASS native data, can produce wrong results with input vector maps created by v.external.See v.db.connect for an example of maintaining attributes in external DBMS in also writable mode.
REFERENCES¶
OGR vector library C API documentationSEE ALSO¶
v.external.out, v.clean, v.db.connect, v.import, v.in.db, v.in.ogr, v.out.ogrOGR Library
PostGIS
See also GRASS user wiki page for more examples.
AUTHORS¶
Radim Blazek, ITC-Irst, Trento, ItalyPostGIS support by Martin Landa, Czech Technical University in Prague, Czech Republic
Last changed: $Date: 2016-01-13 10:18:55 +0100 (Wed, 13 Jan 2016) $
SOURCE CODE¶
Available at: v.external source code (history)Main index | Vector index | Topics index | Keywords index | Graphical index | Full index
© 2003-2016 GRASS Development Team, GRASS GIS 7.2.0 Reference Manual
GRASS 7.2.0 |