Archive for the ‘road-network’ Category

I’ve long been on the search for a free, national road network GIS dataset for Australia. The search has been surprisingly difficult.

If you expect like me that the government would produce an official, national road network GIS database, then your expections are about the be dashed. In Australia, the maintenance of roads, and therefore their corresponding GIS datasets is a state responsibility. This means that there is no single, national official road network produced by the federal government. Even the data owned by state governments is not generally made freely available. While it is sometimes possible to contact state governments and receive a copy of a statewide road network, if you want to assemble a national road network the process has to be repeated for all states and territories. Furthermore, government derived networks generally have onerous licensing terms that mean they cannot be redistributed.

So what data sources are available? I have experience with four:

1. The canonincal combination of state-government road networks is produced by the Public Sector Mapping Agency (PSMA) Australia. Their Transport and Topography product, released quarterly, has been derived from the relevant bodies from each Australian State and Territory jurisdiction as well as the Commonwealth mapping agency. The major advantage of the Transport & Topography dataset is that it is up to date. PSMA also attempt to maintain consistency in attributes across the state derived networks (with varying degrees of success in my experience). Furthermore, PSMA attempt to correct spatial topology errors and perform automated quality assurance. Transport & Topography also has road names that are compatible with the address names in PSMA’s excellent Geocoded National Address File (G-NAF), which is an additional bonus. The downside is that it is very expensive, and its redistribution terms are restrictive.

2. A time-honoured source of road network data is VMAP0. VMAP0, short for Vector Map level 0, is a global data set, declassified by the US National Geospatial Intelligence Agency. VMAP0 was created from the digitisation of military navigational charts, and is perhaps still the most comprehensive global data set for topographic map data that is freely available. That said, there are two major problems with this dataset. First, because it was created from 1:1,000,000 scale maps, the road network is very sparse, meaning even some major roads are not listed. Second, VMAP0 has not been updated for twenty years! The advantage of this dataset is that it is public domain licensed, meaning you can do what ever you like with it. VMAP0 for Australia is available from the USA National Imagery and Mapping Agency, but requires software that can read its funky format like OGR. I believe ESRI also used to distribute VMAP0 shapefiles branded as the Digital Chart of World.

3. The new kid on the block is OpenStreetMap (OSM). OSM uses data contributed by volunteers (a.k.a. ‘Volunteered Geographical Information’ or VGI) to build up a rich spatial database (think Wikipedia for maps). While they are perhaps best known for delivering Google Maps like tiles on their website, you can also download their raw data. The good people at CloudMade take the raw OSM data, convert it to a number of accessible formats, split it up by country and make it available for download on their website. I am hesitant to use this data at the moment, I as don’t know how about its completeness in Australia, or how to selected out roads and not footpaths, for example. However, this has the potential to be a real competitor with Transport & Topography in terms of its currency and completeness, so I’m keen to learn more from anyone using OSM road network data in GIS analysis.

4. Finally, Geoscience Australia (GA) has a series of vector layers that is uses to produce 1:250,000 topographic maps for the whole continent. These are excellent data, consistent and well-curated, but with a couple of caveats. First, because these layers were created for topographic mapping, they are only at a course level of detail. Not all roads are included, particularly in residential areas, and those that are may have been moved in the cartographic production process to stop them from overlapping. Second, these data were last updated in June 2006, meaning that for some purposes they will be too old. Nevertheless, Australia’s national road system doesn’t change that fast, so for some purposes this will be an ideal dataset. Best of all, in 2009, GA relicensed this previously proprietary dataset to the Creative Commons 3.0 by-attribution license, meaning that you can use it, redistribute it and derive your own products from it, as long as you acknowledge Geoscience Australia as the original custodian. These data are freely available at the national scale in ArcGIS Personal Geodatabase format from GA although if you want pre-made shapefiles you’ll have to download individual map grids or buy their product.

If you know of any other national road networks for Australia, let me know.