Sun 19 December 2010
OGR 1.8 introduces support for reading GML with feature attributes expressed as nested elements as found in Ordnance Survey's OS MasterMap as well as support for accessing WFS. This is a brief script for building OGR (GDAL) 1.8 from source as it's not currently released: Download latest daily source export: http://www.gdal.org/daily/ and extract it's contents to a directory you have read, write and execute permissions in (I chose ~/Software/gdal-svn-trunk-2010.12.19) Ensure you have the tools required to build software using make:
sudo apt-get install build-essential
Install the development package for Xerces-C:
sudo apt-get install libxerces-c-dev
Install the PostgreSQL development tools package:
sudo apt-get install libpq-dev
Install curl and the development package:
sudo apt-get install curl libcurl4-gnutls-dev
Change to the directory where you extracted the GDAL source (that's ~/Software/gdal-svn-trunk-2010.12.19 for me):
cd ~/Software/gdal-svn-trunk-2010.12.19
Run the configure script which prepares the ground before we build GDAL with make. Here we are specifying that we want to configure the build to include xerces support and PostgreSQL (/usr/bin/pg_config is a script provided with the PostgreSQL development tools package).
./configure --with-xerces=yes --with-pg=/usr/bin/pg_config --with-curl=/usr/bin/curl-config > configure-output.txt
Now we can actually build GDAL/OGR:
Providing make did not error GDAL should now be built and ready to use. You can find the executable utilities such as gdalinfo, ogrinfo, ogr2ogr etc. in the apps directory within the directory that you extracted the GDAL source (~/Software/gdal-svn-trunk-2010.12.19/apps/ogr2ogr for me.); to make it easier to run these utilities it may be worthwhile setting a variable to this path:
GDAL_PATH=~/Software/gdal-svn-trunk-2010.12.19/apps/
It's also worth setting the GDAL_DATA environment variable so that resources such as coordinate system definitions etc.
export GDAL_DATA=$GDAL_PATH../data
You can then use the utilities like so: Translate from GML to ESRI Shape. To parse nested feature attributes you will need to modify the .gfs file generated the first time the GML file is opened. The .gfs file allows you to map GML properties to feature attributes.
$GDAL_PATH/ogr2ogr -f 'ESRI Shapefile' . test.gml
Translate GML to PostGIS
$GDAL_PATH/ogr2ogr -f PostgreSQL PG:"dbname='postgis' active_schema=mapbase host='localhost' user='fred' password='itscomplicated'" test.gml
List available layers from a WFS
$GDAL_PATH/ogrinfo -ro WFS:"http://www.tinyows.org/cgi-bin/tinyows"
Get info about all features in a given layer including coordinates
$GDAL_PATH/ogrinfo WFS:"http://www.tinyows.org/cgi-bin/tinyows" tows:world -ro -al
Download all features from a layer and write to a good old ESRI Shape file
$GDAL_PATH/ogr2ogr -f 'ESRI Shapefile' . WFS:"http://www.tinyows.org/cgi-bin/tinyows" tows:world
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