NAME¶
v.external - Creates a new vector as a read-only link to OGR
layer.
KEYWORDS¶
vector, external, import
SYNOPSIS¶
v.external
v.external help
v.external [-
f] [
dsn=
string]
[
output=
name] [
layer=
string] [--
overwrite]
[--
verbose] [--
quiet]
Flags:¶
- -f
-
List supported formats and exit
- --overwrite
-
Allow output files to overwrite existing files
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
Parameters:¶
- dsn=string
-
OGR datasource name. Examples:
ESRI Shapefile: directory containing shapefiles MapInfo File: directory
containing mapinfo files
- output=name
-
Output vector. If not given, available layers are printed only.
- layer=string
-
OGR layer name. If not given, available layers are printed only. Examples:
ESRI Shapefile: shapefile name MapInfo File: mapinfo file name
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.
ESRI Shapefile
Mapinfo File
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 maps (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 writable 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: 2012-02-25 14:38:11 +0100 (Sat, 25 Feb 2012) $
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