## DESCRIPTION

v.out.ogr converts GRASS vector map layer to any of the supported OGR vector formats (including OGC GeoPackage, ESRI Shapefile, SpatiaLite or GML).

OGR (Simple Features Library) is part of the GDAL library, so you need to install this library to use v.out.ogr.

The OGR library supports many various formats including:

- OGC GeoPackage
- ESRI Shapefile
- PostGIS
- SpatiaLite
- CSV
- GML
- KML
- Mapinfo File
- TIGER
- ... and many others

The list of supported formats is printed with the -l flag.

For further available other supported formats go here.

## NOTES

By default, islands will appear as holes inside surrounding areas. To export polygons with holes into, e.g., a Esri Shapefile, and make the holes appear as filled areas, the flag -c has to be used.

v.out.ogr exports 3D vector data as 2.5D simple features if possible (not supported by all formats). For exporting 3D vector data as 2D simple features, use -2 flag.

By default, v.out.ogr converts GRASS vector data to single simple features. If GRASS feature has more categories defined in the given layer, then this feature is exported multiple times. GRASS features without category are skipped by default. To export features also without category, the -c flag must be given.

When -m flag is given, v.out.ogr export GRASS vector data as multi-features. Multi-feature is formed by GRASS features with the same category. When -c flag is given, the module also export GRASS features without category as one multi-feature. Note that multi-features are not supported by all formats.

ESRI Shapefile export: note that due to the DBF table specifications column names may not be longer than 10 characters.

Performance: export to SQLite based formats including OGC GeoPackage may become faster with the environmental variable `OGR_SQLITE_CACHE=1024` being set (value depends on available RAM, see OGR ConfigOptions).

## EXAMPLES

### Export to OGC GeoPackage

Export lines from a GRASS vector map to OGC GeoPackage format:

    v.out.ogr input=roadsmajor type=line output=roadsmajor.gpkg

Export areas from GRASS vector map to OGC GeoPackage format, converting islands (holes) to filled polygons:

    v.out.ogr -c input=areas_islands type=area output=areas_islands.gpkg

Export mixed geometry type GRASS vector map to OGC GeoPackage format:

    v.out.ogr input=generic_vector output=mixed_geometry.gpkg

### Export to ESRI Shapefile

Export lines from GRASS vector map to Shapefile format:

    v.out.ogr input=roadsmajor type=line format=ESRI_Shapefile output=lines.shp

Export areas from GRASS vector map to Shapefile format, converting islands (holes) to filled polygons:

    v.out.ogr -c input=areas_islands type=area format=ESRI_Shapefile output=areas_islands.shp

Export 3D lines from GRASS vector map to Shapefile format:

    v.out.ogr input=lines_3d type=line format=ESRI_Shapefile output=lines_3d.shp lco="SHPT=ARCZ"

Export 3D points (e.g., Lidar points) from GRASS vector map to Shapefile format

    v.out.ogr points_3d type=point format=ESRI_Shapefile output=points_3d.shp lco="SHPT=POINTZ"

Export 3D faces from GRASS vector map to Shapefile format:

    v.out.ogr input=objects_3d type=face format=ESRI_Shapefile output=faces_3d.shp lco="SHPT=POLYGONZ"

Export 3D faces from GRASS vector map to Shapefile format, automatic 3D setting:

    v.out.ogr input=objects_3d type=face format=ESRI_Shapefile output=faces_3d.shp"

### Export to GML

Export lines from GRASS vector map to GML format (generates '/tmp/testogr.gml' file with layer 'testogr'):

    v.out.ogr input=multi type=line output=/tmp/testogr.gml output_layer=testogr format=GML

### Export to PostgreSQL/PostGIS

Export areas from GRASS vector map to PostGIS database:

    v.out.ogr input=polygons type=area output="PG:host=localhost dbname=postgis user=postgres" output_layer=polymap format=PostgreSQL

Note: For exporting GRASS vector data to PostGIS database can be also used v.out.postgis module. This module is not based on OGR library and supports beside simple features also topological format (PostGIS Topology).

### Export to KML (Google Earth)

Export faces (3D vectors) from GRASS vector map to KML format for Google Earth:

    v.out.ogr input=buildings_3d output=buildings_3d.kml output_layer=buildings_3d format=KML type=face

Generate and export GRASS vector "asteroid" map (faces, 3D vectors) to KML format for Google Earth:

    # near Raleigh (NC, USA)
    g.region n=35.73952587 s=35.73279182 w=-78.68263928 e=-78.67499517

    # two layers of random points
    v.random -z output=random3d_a n=10 zmin=0 zmax=200
    v.random -z output=random3d_b n=15 zmin=400 zmax=600

    # merge into one 3D points map
    v.patch input=random3d_a,random3d_b output=random3d

    # generate 3D convex hull
    v.hull input=random3d output="random3d_hull"

    # export to KML 3D
    v.out.ogr input=random3d_hull output=random3d_hull.kml format=KML type=face dsco="AltitudeMode=absolute"

    # now open KML file 'random3d_hull.kml' in Google Earth or NASA WorldWind or ...

## REFERENCES

- OGR vector library
- OGR vector library C API documentation

## SEE ALSO

v.out.postgis, db.out.ogr, v.external, v.external.out, v.in.ogr, v.pack

## AUTHORS

Radim Blazek, ITC-Irst, Trento, Italy
Some contributions: Markus Neteler
Multi-feature support by Martin Landa, Czech Technical University in Prague, 2013

Last changed: $Date$