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A simple loader for geographic data in GML and KML

(that needs some preparation before loading via ogr2ogr)

Author: Matt Walker, Astun Technology Ltd.

Contact: support [at] astuntechnology.com

A simple GML loader written in Python that makes use of OGR 1.8. Source data can be in GML or KML format (including compressed files in GZ or ZIP format) and can be output to any of the formats supported by OGR. The source data can be prepared using a simple Python to both make it suitable for loading with OGR (useful with complex feature types) or to add value by deriving attributes.

The loader was originally written to load Ordnance Survey OS MasterMap Topographic Layer data in GML/GZ format but has since been used to load other GML and KML data.

Dependencies

  • OGR 1.8

    • OGR is part of the GDAL suite of tools for translating and manipulation geospatial data.
    • Windows users can use OSGeo4W (choose Advanced install and select GDAL under the Commandline_Utilities section). You can then run the loader using the OSGeo4W Shell which will have OGR available.
    • Linux users see GDAL Downloads.

  • Python 2.6+ or 3

    • Python 2.6 or above (including 3) is required. Most modern Linux operating systems will already have 2.6 or above. Windows users can download Python from the Python Downloads page.
    • Python lxml module for parsing and manipulating XML, Windows users can download from the lxml project page, Linux users can usually install via their package manager (Ubuntu users would use: sudo apt-get install python-lxml)

Further install details are available on the project wiki

Usage

First configure the loader by editing 'loader.config' specifying:

Basic configuration

  • 'src_dir'
    • The directory containing your source files. All supported files in the specified directory and it's decendents will be loaded.
  • 'out_dir'
    • The directory used to store the translated data if writing to a file based format such as ESRI Shape, MapInfo TAB etc.
  • 'tmp_dir'
    • The directory used to store temporary working files during loading.
  • 'ogr_cmd'
    • The ogr2ogr command that will be used to load the data. Here you can specify the destination format and any associated settings (for example database connection details if you are writing to PostGIS).
  • 'prep_cmd'
    • The command used to prepare the source data so it is suitable for loading with OGR, choose one that is suitable for your source data such as prep_osgml.prep_osmm_topo for OS MasterMap Topo.
  • 'gfs_file'
    • OGR .gfs file used to define the feature attributes and geometry type of the feautes read from the GML again choose a suitable gfs file for your source data such as ../gfs/osmm_topo_postgres.gfs for loading OS MasterMap Topo in to PostgreSQL.

Note: Environment variables can be used with any of the options by using a token of the form: $HOME, ${HOME} or %TEMP% (Windows only)

Then run from the commandline:

'python loader.py loader.config'

Additional arguments can be passed to override the values in the config file (useful when running more than one instance of the loader) for example to specify a different source directory ('src_dir'):

'python loader.py config_file src_dir=./data/tq'

Some configuration examples are available on the project wiki

To-do

  • Documentation

    • Use of environment variables in the config file
    • Document the available tokens that can be used in the ogr_cmd, post_cmd
    • Using an alternative Python interpretor with OSGeo4W by specifying PYTHONHOME and the full path to the interpretor on Windows

  • loader.py

    • Add exception and message when source data is not found

  • OS MasterMap ITN

    • Test load on national cover
    • PostgreSQL scripts to join it all up