[[TOC]]
= OGR interface in GRASS 7 =

See also [http://grass.osgeo.org/wiki/Working_with_external_data_in_GRASS_7#Vector_data examples] from GRASS [http://grass.osgeo.org/wiki 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 [http://www.youtube.com/watch?v=DTMmmcVpJKk export GRASS data to PostGIS] using [http://grass.osgeo.org/wiki/WxGUI_Modeler 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 [source: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 [source:grass/trunk/lib/vector/Vlib/write_ogr.c 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 ==

 * [http://trac.osgeo.org/gdal/ticket/4202 #4202]
 * [http://trac.osgeo.org/gdal/ticket/4217 #4217]