OGR interface in GRASS 7

See also ​examples from GRASS ​User Wiki.

Direct OGR read access

Capability to read OGR layers directly without linking them via v.external.

Example 1: Shapefile 'busstopsall.shp' located in directory '~/shapefiles'

v.info map=~/shapefiles/@OGR layer=busstopsall

Example 2: PostGIS table 'busstopsall' located in database 'pgis_nc'.

v.extract input=PG:dbname=pgis_nc@OGR layer=busstopsall where="STREET_1 = 'William Moore Dr.'" output=b1

List of modules which supports direct OGR read access ((*) indicates work in progress):

• v.info (r39161), v.db.connect (r39538), v.extract (r39621), v.db.select (r39556), v.buffer (r39809), v.category (r39812), v.class (r39813), v.clean (r39814), v.delaunay (r39821), v.dissolve (r39822), v.distance (r39823), v.drape (r39826), v.extrude (r39827), v.generalize (r39828), v.hull (r39829), v.kcv (r39832), v.neighbors (r39834), v.normal (r39839), v.out.ascii (r39881), v.out.dxf (r39882), v.out.ogr (r39883), v.out.pov (r39884), v.out.svg (r39885), v.overlay (r39895), v.parallel (r39896), v.pertrub (r39897), v.qcount (r39898), v.report (r39905), v.sample (r39906), v.segment (r39907), v.reclass (r39908), v.random (r39909), v.rast.stats (r39910), v.split, v.surf.idw, v.surf.rst, v.to.3d, v.to.db, v.to.points, v.to.rast, v.to.rast3, v.transform, v.type, v.univar, v.what (r40188), v.select (r48936)

Direct OGR write access

Capability to write OGR layers directly without need to store data in the native GRASS vector format and then exporting data using v.out.ogr.

Testcase:

• GRASS location: nc_spm_08 - ​http://grass.osgeo.org/sampledata/nc_spm_latest.tar.gz
• Shapefile directory: ~/shapefiles - ​http://grass.osgeo.org/sampledata/north_carolina/nc_shape.tar.gz
• PostGIS database: pgis_nc (see how to ​export GRASS data to PostGIS using ​wxGUI Modeler)

Scenario 1 (not implemented)

Use parameters output for output OGR datasource and olayer for OGR layer. Example:

# input: GRASS data
# output: PostGIS database
v.extract input=bridges where="BRIDGE_NUM=417" output=bridges_417

# input: PostGIS layer, ESRI Shapefile
# output: PostGIS database
v.select ainput=PG:dbname=gisdb@OGR alayer=zeleznice \
 binput=shps@OGR blayer=obce operator=intersects \
 output=PG:dbname=gisdb@OGR olayer=obce_zelez

Status: not planned to be implemented

Scenario 2 (implemented)

Design v.external.out (similarly to r.external.out)

# input: GRASS data
# output: PostGIS database
v.external.out dsn=PG:dbname=pgis_nc format=PostgreSQL
v.extract input=bridges where="BRIDGE_NUM=417" output=bridges_417

# input: PostGIS layer, ESRI Shapefile
# output: PostGIS database
v.select ainput=PG:dbname=pgis_nc@OGR alayer=roadsmajor \
 binput=~/shapefiles@OGR blayer=boundary_municp operator=intersects \
 output=municp_roads

Status: implemented grass/trunk/vector/v.external.out

Tasks

• Attribute table (write) access for OGR-linked vectors (direct or linked by v.external)
  • Implemented in r47225

Changes in vector library

See write_ogr.c​

• New functions - V1_write_line_ogr(), V2_write_line_ogr(), V1_rewrite_line_ogr(), V2_rewrite_line_ogr(), V1_delete_line_ogr(), V2_delete_line_ogr()
• Vect_build_ogr() support all build levels - r48960
• Implement V2__add_line_to_topo_ogr() - r49178

Current status

Module	Read access (link)	Direct read access	Direct write access
v.build	Y	N	N
v.build.all	Y	N	N
v.clean	Y	Y	N
v.edit	Y	Y	Y
v.extract	Y	Y	Y
v.out.dxf	Y	Y	N
v.select	Y	Y	Y
v.random	Y	Y	Y
v.voronoi	Y	Y	N
v.what	Y	Y	X
v.what.rast	Y	Y	Y
v.what.vect	Y	Y	Y

Related OGR tickets

• ​#4202
• ​#4217