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v.external: Creates a new vector as a read-only link to OGR layer. Available drivers: ESRI Shapefile,MapInfo File,UK

v.external - Creates a new vector as a read-only link to OGR layer. Available drivers: ESRI Shapefile,MapInfo File,UK .NTF,SDTS,TIGER,S57,DGN,VRT,REC,Memory,BNA,CSV,GML,GPX,KML,GeoJSON,GMT,SQLite,ODBC,PGeo,OGDI,PostgreSQL,MySQL,XPlane,AVCBin,AVCE00,Geoconcept


v.external v.external help v.external dsn=string [output=name] [layer=string] [--overwrite] [--verbose] [--quiet] Flags: --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


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 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.


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


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.
OGR vector library OGR vector library C API documentation
v.clean, v.db.connect, v.in.db, v.in.ogr, v.out.ogr


Radim Blazek, ITC-Irst, Trento, Italy Last changed: $Date: 2006-03-21 19:22:37 +0100 (Tue, 21 Mar 2006) $ Full index (C) 2003-2010 GRASS Development Team V.EXTERNAL(1)

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