Guest Post: On the Value of Open Roof Prints

Allan Barger

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At the end of 2013 the City of Greater Geelong published the first dataset to utilise our newely installed geoserver. We asked them to let us know their experiences so far and this guest post comes to us from Martin von Wyss who is the Co-ordinator for their Spatial Information Services group. Many thanks Martin for sharing your experiences.

In late 2013 the City of Greater Geelong published the first of its GIS data layers to While preparing the information, which describes the building outlines, we also worked to change our data licence agreement policy so that it’d be easier to share the information in a way that’s clear, painless, and in line with other Australian government agencies. As a result, Geelong Council changed our policy from a wordy 6-page document that required two parties to sign to the CCBY AU 3.0 standard.

In the short time since the data became available, we’ve identified four tangible benefits from open data hosted by

First and foremost, putting the data online has reduced the amount of work required in sharing the information. A few hours of data preparation and a few well-targeted emails mean that private architecture firms and members of the architecture community at the local university have been able to access the information by themselves. Not only can users access the information without troubling us with data requests, but we also save time by not having to process paperwork thanks to the Creative Commons licence.

Innovation is one of the four core values in Council. While Open Data is not a new or innovative concept anymore, for an organisation that has been keeping its data closely guarded the idea of sharing our building roofprints is innovative. “Geelong’s future is as a 21st century smart city,” says the mayor of Geelong, and this is a tangible example of how we’re working to this goal.

Internally we hope that the publication of the data to the world will make it easier to convince custodians of other Geelong GIS data that it’s OK to release information. The published data was commissioned by and falls under the custodianship of the spatial information services group, whereas most of Council‘s data is in the hands of disparate departments. We’re optimistic that when others see our willingness to share our own information via the CCBY licence, their apprehensions will fall away.

Finally, an unanticipated benefit of the publication of our data was the scrutiny directed at the data by the public. Members of the Open Street Map community are trying to bring the data into their environment as 3d models of buildings. Their modus operandi is to move small chunks of data into the OSM database. The small section with which they began lined up very poorly with the underlying orthophotography. I suspected a datum or projection error had crept into the process of publishing the data, and I examined all the steps I had gone through before uploading the file. I found no errors, so I checked with the hosts of to see if there could have been an error introduced in their processes. Alex then found a blog on an OSM page which drew the attention to the possibility that the imagery in Bing Maps which forms the background to the OSM data publishing environment “may be misaligned” at large-scale zoom levels.

It’s only natural that the OSM community and I would assume that imagery—to which we can relate because it looks familiar—would be accurate and that the abstracted data are in the wrong place. In this case that doesn’t seem to be the case but it’s undoubtedly a very good thing that many critical eyes are evaluating our data thanks to its exposure on

We’re optimistic that our data will improve services, products and local knowledge to make Geelong a better place to live. Thanks to for the opportunity to contribute our data for public use and consumption.

Martin von Wyss
Co-ordinator, Spatial Information Services


Comments (1)

The Open Street Map community has taken Geelong's building roofprints and mapped them in OSM. They look particularly good in the F4 Map, a WebGL map.

Last updated: 17 August 2016