<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>GRASS GIS: v.external</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" href="grassdocs.css" type="text/css"> </head> <body bgcolor="white"> <img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade> <h2>NAME</h2> <em><b>v.external</b></em> - Creates a new vector as a read-only link to OGR layer.<BR> Available drivers: ESRI Shapefile,MapInfo File,UK .NTF,SDTS,TIGER,S57,DGN,VRT,REC,Memory,BNA,CSV,GML,GPX,KML,GeoJSON,Interlis 1,Interlis 2,GMT,SQLite,DODS,ODBC,PGeo,OGDI,PostgreSQL,MySQL,XPlane,AVCBin,AVCE00,GRASS,Geoconcept <h2>KEYWORDS</h2> vector <h2>SYNOPSIS</h2> <b>v.external</b><br> <b>v.external help</b><br> <b>v.external</b> <b>dsn</b>=<em>string</em> [<b>output</b>=<em>name</em>] [<b>layer</b>=<em>string</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>] <h3>Flags:</h3> <DL> <DT><b>--overwrite</b></DT> <DD>Allow output files to overwrite existing files</DD> <DT><b>--verbose</b></DT> <DD>Verbose module output</DD> <DT><b>--quiet</b></DT> <DD>Quiet module output</DD> </DL> <h3>Parameters:</h3> <DL> <DT><b>dsn</b>=<em>string</em></DT> <DD>OGR datasource name. Examples:<br> ESRI Shapefile: directory containing shapefiles<br> MapInfo File: directory containing mapinfo files</DD> <DT><b>output</b>=<em>name</em></DT> <DD>Output vector. If not given, available layers are printed only.</DD> <DT><b>layer</b>=<em>string</em></DT> <DD>OGR layer name. If not given, available layers are printed only. Examples:<br> ESRI Shapefile: shapefile name<br> MapInfo File: mapinfo file name</DD> </DL> <h2>DESCRIPTION</h2> <em>v.external</em> creates new vector as a link to external <a href="http://www.gdal.org/ogr/">OGR</a> layer (read only). OGR (Simple Features Library) is part of the <a href="http://www.gdal.org">GDAL</a> library, so you need to install GDAL to use <em>v.external</em> and external OGR layers. <P> <h3>Supported OGR Vector Formats</h3> <a href="http://www.gdal.org/ogr/drv_shapefile.html">ESRI Shapefile</a><br> <a href="http://www.gdal.org/ogr/drv_mitab.html">Mapinfo File</a> <p> 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 <a href="http://www.gdal.org/ogr/ogr_formats.html">OGR web site</a>. <h2>EXAMPLES</h2> <B>SHAPE files</B><BR> <div class="code"><pre> v.external dsn=/home/user/shape_data layer=test_shape output=grass_map </pre></div> <P> <B>MapInfo files</B><BR> <div class="code"><pre> v.external dsn=./ layer=mapinfo_test output=grass_map </pre></div> <P> <B>SDTS files</B> (you have to select the CATD file)<BR> <div class="code"><pre> v.external dsn=CITXCATD.DDF output=cities </pre></div> <P> <B>TIGER files</B><BR> <div class="code"><pre> v.external dsn=input/2000/56015/ layer=CompleteChain,PIP output=t56015_all </pre></div> <P> <B>PostGIS maps (area example)</B><BR> <div class="code"><pre> v.external dsn="PG:host=localhost user=postgres dbname=postgis" layer=polymap \ output=polygons </pre></div> <P> <H2>NOTES</H2> 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 <em>v.external</em>. <p> See <a HREF="v.db.connect.html">v.db.connect</a> for an example of maintaining attributes in external DBMS in also writeable mode. <H2>REFERENCES</H2> <a href="http://www.gdal.org/ogr/">OGR vector library</a> <br> <a href="http://www.gdal.org/ogr/ogr__api_8h.html">OGR vector library C API</a> documentation <h2>SEE ALSO</h2> <em><a HREF="v.clean.html">v.clean</a></em>, <em><a HREF="v.db.connect.html">v.db.connect</a></em>, <em><a HREF="v.in.db.html">v.in.db</a></em>, <em><a HREF="v.in.ogr.html">v.in.ogr</a></em>, <em><a HREF="v.out.ogr.html">v.out.ogr</a></em> <h2>AUTHOR</h2> Radim Blazek, ITC-Irst, Trento, Italy <p><i>Last changed: $Date: 2006-03-21 19:22:37 +0100 (Tue, 21 Mar 2006) $</i> <HR> <P><a href="index.html">Main index</a> - <a href="vector.html">vector index</a> - <a href="full_index.html">Full index</a></P> <P>© 2003-2008 <a href="http://grass.osgeo.org">GRASS Development Team</a></p> </body> </html>
