Category Archives: Vector

New stable release of GRASS GIS 7.0.0!

The GRASS GIS Development team has announced the release of the new major version GRASS GIS 7.0.0. This version provides many new functionalities including spatio-temporal database support, image segmentation, estimation of evapotranspiration and emissivity from satellite imagery, automatic line vertex densification during reprojection, more LIDAR support and a strongly improved graphical user interface experience. GRASS GIS 7.0.0 also offers significantly improved performance for many raster and vector modules: “Many processes that would take hours now take less than a minute, even on my small laptop!” explains Markus Neteler, the coordinator of the development team composed of academics and GIS professionals from around the world. The software is available for Linux, MS-Windows, Mac OSX and other operating systems.

Detailed announcement and software download:

The Geographic Resources Analysis Support System (, commonly referred to as GRASS GIS, is an open source Geographic Information System providing powerful raster, vector and geospatial processing capabilities in a single integrated software suite. GRASS GIS includes tools for spatial modeling, visualization of raster and vector data, management and analysis of geospatial data, and the processing of satellite and aerial imagery. It also provides the capability to produce sophisticated presentation graphics and hardcopy maps. GRASS GIS has been translated into about twenty languages and supports a huge array of data formats. It can be used either as a stand-alone application or as backend for other software packages such as QGIS and R geostatistics. It is distributed freely under the terms of the GNU General Public License (GPL). GRASS GIS is a founding member of the Open Source Geospatial Foundation (OSGeo).

OGR vector data tips and tricks

Get vector map extent

You can easily grep the map extent of a vector map (bounding box):

ogrinfo /cdrom/ITALY_GC.SHP ITALY_GC | grep Extent
Extent: (9.299460, 43.787362) – (13.911350, 47.070188)

Merge of two SHAPE files

Merge of two SHAPE files ‘file1.shp’ and ‘file2.shp’ into a new file ‘file_merged.shp’ is performed like this:

ogr2ogr file_merged.shp file1.shp
ogr2ogr -update -append file_merged.shp file2.shp -nln file_merged file2

The second command is opening file_merged.shp in update mode, and trying to find existing layers and append the features being copied. The -nln option sets the name of the layer to be copied to.

Vector map reprojection

We reproject from the source projection (as defined in .prj file) to WGS84/LL:

ogr2ogr vmap0rd_ll.shp -t_srs “EPSG:4326” vmap0rd.shp

If the .prj file is missing, you can use the ‘’ utility to create it if you know the EPSG code: -wkt 4326 > cities.prj

Reproject to current GRASS location projection:

ogr2ogr -t_srs “`g.proj -wf`” polbnda_italy_GB_ovest.shp polbnda_italy_LL.shp

Cut out a piece of a vector map
Use spatial query extents: -spat xmin ymin xmax ymax (W S E N)

ogr2ogr ARC_BZ.shp -spat 10 45 13 47 ARC.shp

Get VMAP0 metadata info:

ogrinfo -ro gltp:/vrf/grass0/warmerdam/v0soa/vmaplv0/soamafr
ogrinfo -ro gltp:/vrf/grass0/warmerdam/v0soa/vmaplv0/soamafr | grep bnd
ogrinfo -ro gltp:/vrf/grass0/warmerdam/v0soa/vmaplv0/soamafr ‘polbnda@bnd(*)_area’
ogrinfo -ro gltp:/vrf/grass0/warmerdam/v0eur/vmaplv0/eurnasia ‘roadl@trans(*)_line’

MAP0: Extract spatial subregion, reproject from NAD83 to WGS84

# coordinate order: W S E N
ogr2ogr -spat 19.95035 -26.94755 29.42989 -17.72624 -t_srs ‘EPSG:4326’ \
polbnda_botswana.shp gltp:/vrf/grass0/warmerdam/v0soa/vmaplv0/soamafr \


Sample ‘where’ statements (use -sql for PostgreSQL driver):

# -where ‘fac_id in (195,196)’
# -where ‘fac_id = 195’
ogrinfo -ro -where ‘fac_id in (195,196)’ \
gltp:/vrf/grass0/warmerdam/v0soa/vmaplv0/soamafr ‘polbnda@bnd(*)_area’

VMAP0 examples

Find out the Countries VMAP0 coding:

ogdi_info -u gltp:/vrf/grass0/warmerdam/v0soa/vmaplv0/soamafr \
-l ‘polbnda@bnd(*)_area’ -f area | grep Botswana

or read the VMAP0 Military specs, page 75

Extract Botswana, reproject on the fly from NAD83 to WGS84, store as SHAPE:

ogr2ogr -t_srs “EPSG:4326” -where “na2 = ‘BC'” polbnda_botswana.shp \
gltp:/vrf/grass0/warmerdam/v0soa/vmaplv0/soamafr ‘polbnda@bnd(*)_area’

Extract Germany, reproject on the fly from NAD83 to WGS84, store as SHAPE:

ogr2ogr -t_srs “EPSG:4326” -where “na2 = ‘GM'” polbnda_germany.shp
gltp:/vrf/grass0/warmerdam/v0eur/vmaplv0/eurnasia ‘polbnda@bnd(*)_area’
ogrinfo -summary polbnda_germany.shp polbnda_germany | grep Extent
# Extent: (5.865639, 47.275776) – (15.039889, 55.055637)
# W S E N

VMAP0 Contour lines for Germany:

ogr2ogr -t_srs “EPSG:4326” -spat 5.865639 47.275776 15.039889 55.055637 \
contour_lines.shp \
gltp:/vrf/grass0/warmerdam/v0eur/vmaplv0/eurnasia ‘contourl@elev(*)_line’

VMAP0 elevation spots (points) for Germany:

ogr2ogr -t_srs “EPSG:4326” -spat 5.865639 47.275776 15.039889 55.055637 \
elevation_spots.shp \
gltp:/vrf/grass0/warmerdam/v0eur/vmaplv0/eurnasia ‘elevp@elev(*)_point’

VMAP0 lakes of Trentino province in Italy:

ogr2ogr -t_srs “EPSG:4326” -where “na2 = ‘IT'” \
-spat 10.340029 45.261888 10.98727 45.98993 \
lakes_italy.shp \
gltp:/vrf/grass0/warmerdam/v0eur/vmaplv0/eurnasia ‘inwatera@hydro(*)_area’

Connect OGR and PostgreSQL/PostGIS

ogrinfo PG:’ user=postgres dbname=ogc_simple’
ogr2ogr out.shape PG:’ user=postgres dbname=ogc_simple’ lake_geom


Convert GRASS 6 vector map to SHAPE (needs GDAL-OGR-GRASS plugin):

# -nln is “new layer name” for the result:
ogr2ogr archsites.shp grassdata/spearfish60/PERMANENT/vector/archsites/head 1 \
-nln archsites

Using WKT files with ogr2ogr

The definition is in ESRI WKT format. If you save it to a text file called out.wkt you can do the following in a translation to reproject input latlong points to this coordinate system:

ogr2ogr -s_srs WGS84 -t_srs ESRI::out.wkt out_dir indatasource

Most comand line options for GDAL/OGR tools that accept a coordinate system will allow you to give the name of a file containing WKT. And if you prefix the filename with ESRI:: the library will interprete the WKT as being ESRI WKT and convert to “standard” format accordingly. The -s_srs switch is assigning a source coordinate system to your input data (in case it didn’t have this properly defined already), and the -t_srs is defining a target coordinate system to reproject to.

TIGER files in OGR

# linear features:
ogr2ogr tiger_lines.shp tgr46081.rt1 CompleteChain

# area features:
export PYTHONPATH=/usr/local/lib/python2.5/site-packages tgr46081.rt1 tiger_area.shp

OGR CSV driver: easily indicate column types

You can now write a little csv help file to indicate the columns types to OGR. It works as follows. Suppose you have a foobar.csv file that looks like this:


Now write a foobar.csvt file like this one:


The driver will then use the types you specified for the csv columns. The types recognized are Integer, Real and String, DateTime, and Date.

Convert KML to CSV (WKT)

First find layers:

ogrinfo -so myfile.kml

Then convert KML to CSV:

ogr2ogr -f CSV out.csv myfile.kml -sql “select *,OGR_GEOM_WKT from myfilelayer”
cat out.csv

Or use the cool online converter:

d.vect: support for z height (geometry) colors added

After getting mad with Lidar points colorizing which till now
required a DB table with GRASSRGB attributes, I have
modified d.vect to support colors directly from z height (geometry).
Works for 3D points, lines (eg, 3D contours) and 3D polygons
(eg delaunay triangles):

# Spearfish:
g.region rast=elevation.10m
r.random elevation.10m n=5000 vector=random3d -d
d.mon x0
# display as black points
d.vect random3d
# display 3D points colorized according to z height
d.vect -z random3d zcol=gyr

# 3D contour lines
r.contour elevation.10m out=contour20m step=20
d.vect -z contour20m zcol=gyr

# generate 3D triangles
v.delaunay random3d out=random3d_del
# display 3D polygons colorized according to z height
d.vect -z random3d_del type=area zcol=gyr