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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, PostGIS

SYNOPSIS

   v.external
   v.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, type
   v.external -f
   For 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 file
   v.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 documentation

AUTHORS

   Radim Blazek, ITC-Irst, Trento, Italy
   PostGIS  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

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