--- name: "v.out.postgis" section: "1grass" platform: "linux" package: "grass-doc" version: "8.4.1-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/v.out.postgis" --- # v.out.postgis(1grass) Exports a vector map layer to PostGIS feature table. ## NAME **v.out.postgis** - Exports a vector map layer to PostGIS feature table. ## KEYWORDS vector, export, output, PostGIS, simple features, topology, 3D ## SYNOPSIS **v.out.postgis**\ **v.out.postgis --help**\ **v.out.postgis** \[-**tl2**\] **input**=*name* \[**type**=*string*\[,*string*,...\]\] \[**layer**=*string*\] **output**=*string* \[**output\_layer**=*name*\] \[**output\_link**=*name*\] \[**options**=*key=value*\[,*key=value*,...\]\] \[--**overwrite**\] \[--**help**\] \[--**verbose**\] \[--**quiet**\] \[--**ui**\] ### Flags: - **-t** Do not export attribute table - **-l** Export PostGIS topology instead of simple features - **-2** Force 2D output even if input is 3D\ Useful if input is 3D but all z coordinates are identical - **--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**=*name* **\[required\]** Name of input vector map - **type**=*string\[,string*,...\] Input feature type\ Options: *point, line, boundary, centroid, area, face, kernel, auto*\ Default: *auto* - **layer**=*string* Layer number or name\ Default: *1* - **output**=*string* **\[required\]** Name for output PostGIS datasource\ Starts with ’PG’ prefix, eg. ’PG:dbname=grass’ - **output\_layer**=*name* Name for output PostGIS layer\ If not specified, input name is used - **output\_link**=*name* Name for output vector map defined as a link to the PostGIS feature table\ If not specified, the vector link is not created. The link can be also manually created by ’v.external’ module. - **options**=*key=value\[,key=value*,...\] Creation options\ Examples:\         ’FID=cat’: define feature id column ’cat’\         ’GEOMETRY\_NAME=wkb\_geometry’: define geometry column ’wkb\_geometry’\         ’SPATIAL\_INDEX=NO’: do not create spatial index on geometry column ## DESCRIPTION *v.out.postgis* exports an existing GRASS vector map layer to PostGIS feature table. Features without category are skipped. By default GRASS GIS topological features are converted into simple features (see OGC Simple Feature Access specification for details). Flag **-l** allows to export vector features as topological elements stored in PostGIS Topology schema. Note that topological export requires PostGIS version 2 or later. Additional creation options can be defined by **options** parameter: - • `FID=` - name of column which will be used as primary key (feature id), default: `fid` - • `GEOMETRY_NAME=` name of column which will be used for storing geometry data in feature table, default: `geom` - • `SPATIAL_INDEX=YES|NO` - enable/disable creating spatial index on geometry column, default: `YES` - • `PRIMARY_KEY=YES|NO` - enable/disable adding primary key on FID column, default: `YES` - • `SRID=` - spatial reference identifier, default: not defined PostGIS Topology related options (relevant only for **-l** flag): - • `TOPOSCHEMA_NAME=` - name of PostGIS Topology schema, default: `topo_` - • `TOPOGEOM_NAME=` - name of column which will be used for storing topogeometry data in feature table, default: `topo` - • `TOPO_TOLERANCE=` - tolerance for PostGIS Topology schema, see CreateTopology function for details, default: `0` - • `TOPO_GEO_ONLY=YES|NO` - store in PostGIS Topology schema only data relevant to Topo-Geo data model, default: `NO` Creation **options** are comma-separated pairs (`key=value`), the options are case-insensitive. Note that **options** defined by *v.external.out* are ignored by *v.out.postgis*. *v.out.postgis* optionally also creates a new vector map in the current mapset if **output\_link** is defined. ## NOTES By default *v.out.postgis* exports vector data as *simple* *features*, ie. boundaries and centroids (forming topological areas) become polygons, isles become holes. Geometry of simple feature elements is stored in PostGIS feature table in the column named "geom". Name of the geometry column can be changed by **options=**`GEOMETRY_NAME=`. Note that for exporting vector features as simple features can be alternatively used PostgreSQL driver from OGR library through *v.out.ogr* module. Also note that it’s allowed to store in the feature table only features of the same type, ie. mixing of points and lines is not currently possible. The feature type is determined for output feature table from the first vector feature accessing data sequentially (**type=auto**). Vector features of other types are during export skipped. User can choose preferable feature type by **type** parameter. Only single type is currently allowed (see TODO section for details). *v.out.postgis* currently supports only three basic output simple feature types: Points, Linestrings and Polygons. Also 3D features of the same type are supported, eg. 3D points are exported as `PointZ` simple feature. Faces are exported as 3D polygons. 3D features are written to the output automatically if input vector map is 3D. If **-2** flag is given then the output is always 2D (z-coordinate is silently ignored for 3D input vector maps). Multigeometries are not currently supported. Features with the same category are exported as multiple single features. *v.out.postgis* also allows exporting vector features as *topological elements* in PostGIS Topology schema. PostGIS Topology extension uses three tables to store basic topological elements which forms topological objects like areas or isles in GRASS terminology. *Nodes* (0-dimensional topological elements) are stored in "node" table, *edges* (1-dimensional elements) in "edge" table and *faces* (2-dimensional elements) in "face" table. - • GRASS nodes are stored in *node* table - • GRASS points are stored in *node* table as regular nodes - • GRASS centroids are stored in *node* table as regular nodes ("containing\_face" refers to related area) - • GRASS lines are stored in *edge* table - • GRASS boundaries are stored in *edge* table - • GRASS areas are stored in *face* table Tables *node*, *edge* and *face* are stored in given topological schema. By default *v.out.postgis* defines its name as `topo_`. Alternatively, the name for topology schema can be defined by **options=**`TOPOSCHEMA_NAME=`. ## EXAMPLES ### Export Simple Features Export vector map "urbanarea" as feature table "urbanarea" located in database "grass", schema "public". Note that this database schema is automatically used when not defined by the user.\ ``` v.out.postgis input=urbanarea output="PG:dbname=grass" ``` GRASS areas are converted into polygons, isles into holes. We can check the number or created polygons by simple SQL query below.\ ``` db.select driver=pg database=grass \ sql="SELECT ST_GeometryType(geom) as geom_type, count(*) from urbanarea group by geom_type" geom_type|count ST_Polygon|657 ``` *Note:* same procedure can be done by *v.out.ogr* module, eg.\ ``` v.out.ogr input=urbanarea output="PG:dbname=grass" format=PostgreSQL ``` In this case GRASS vector data are exported to PostGIS database using OGR library, namely using PostgreSQL driver. Contrary to the *v.out.ogr* module, *v.out.postgis* is using directly PostGIS data provider which is part of GRASS vector engine. Besides that, *v.out.postgis* is optimized for PostGIS export including topological access to the data. ### Export data into specific database schema Database schema for storing exported data can be defined by **output\_layer** as `.`. If the specified schema doesn’t exist in the database, then it’s automatically created. Export vector map "bridges" as feature table in database schema "grassout".\ ``` v.out.postgis input=bridges output="PG:dbname=grass" output_layer=grassout.bridges ``` ### Export data with creation options Example below demonstrates how to define name for geometry column and disable building spatial index. Spatial reference system is defined by `srid` identifier which corresponds in this case with EPSG 3358 (North Carolina dataset).\ ``` v.out.postgis input=roadsmajor output="PG:dbname=grass" options="GEOMETRY_NAME=wkb_geometry,SPATIAL_INDEX=NO,SRID=3358" ``` ### Link exported data Exported data can be linked as vector map created in the current mapset by specifying **output\_link** parameter. In the example below vector map "busstopsall" from PERMANENT mapset is exported into "grass" PostGIS database. *v.out.postgis* after successful export also creates in the current mapset GRASS vector map as a link to the PostGIS feature table.\ ``` v.out.postgis input=busstopsall@PERMANENT output="PG:dbname=grass" output_link=busstopsall_pg ``` Created link can be checked by *v.info*:\ ``` v.info busstopsall_pg ... |----------------------------------------------------------------------------| | Map format: PostGIS (PostgreSQL) | | DB table: public.busstopsall | | DB name: grass | | Geometry column: geom | | Feature type: point | | Topology: pseudo (simple features) | |----------------------------------------------------------------------------| ... ``` ### Export data without attributes *v.out.postgis* allows ignoring attributes when exporting vector features by specifying **-t** flag. Command below exports vector features without attributes. The feature will contain only two columns, the fid and geometry column.\ ``` v.out.postgis -t input=railroads output="PG:dbname=grass" ``` ### Export topological data By default *v.out.postgis* exports data as simple features. Flag **-l** allows exporting data as topological elements instead of simple features. Export topological elements is stored in PostGIS Topology schema.\ ``` v.out.postgis -l input=busroutesall output="PG:dbname=grass" ``` For more info about PostGIS Topology implementation in GRASS see the wiki page. ## TODO - • Multi-feature export - • Allow mixed features (points, lines) - • Support other simple feature types like GeometryCollection and others - • Implement missing options from *v.out.ogr*: **-a**, **-s**, **-c**, **-p**, **-n** - • Add options: **cats**, **where** ## REQUIREMENTS - • PostGIS 2.x or later for topological export (flag **-l**) ## REFERENCES - • OGC Simple Feature Access specification - • PostGIS Topology documentation - • GRASS-PostGIS data provider ## SEE ALSO *v.out.ogr,* *v.external,* *v.external.out,* *v.in.ogr* See also PostGIS and PostGIS Topology wiki page from GRASS User Wiki. ## AUTHOR Martin Landa, Czech Technical University in Prague, Czech Republic (development supported by Fondazione Edmund Mach and Comune di Trento, Italy) ## SOURCE CODE Available at: v.out.postgis source code (history) Accessed: Monday Feb 24 17:51:21 2025 Main index \| Vector index \| Topics index \| Keywords index \| Graphical index \| Full index © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual