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A workshop will be hosted in Canberra in March by Anzlic, the Australian national mapping council, to improve the definition of heights across the continent.

Anzlic staff have been working towards a National Digital Elevation Model since 2006. Essentially, the problem is just another take on the familiar one of standards and discoverability. There is plenty of perfectly good data that defines most of Australia to within 30 cm or better, but finding out who's got it, who's licensing it, and who's using it is an insurmountable problem.

Currently, the best generally available nationally consistent model is Geoscience Australia's 9-second DEM, which is derived from its 1:250,000 scale mapping. It is also possible to acquire data from NASA's Shuttle Radar Topography Mission at 90 metre spacings. Some military - and other nationally important - users also have access to 30 metre postings from SRTM.

However, there are many applications of extreme national importance that cannot be supported by mapping on this scale. Flood mapping is one such. Measuring the effect of rises in sea level is another.

The multi million dollar payout for recent floods in Mackay and Newcastle has also concentrated the minds of insurance analysts on questions of vertical definition.

Speaking at a conference in Melbourne earlier this week, Anzlic executive director Ian Batley said that more accurate data is technically possible over all of Australia, but economically possible over only small parts of it.

This would matter less if all the data that is acquired was used efficiently. It is not. He said there is wide spread support for a national approach through shared responsibility and co-ordinated resourcing.

Seven regional workshops were conducted last year, and more than 300 users of digital elevation data attended.

Their demand is for national standards for elevation data, and a common vertical datum to be used in new - and where possible, existing - elevation datasets. They also want improved ability to find and access them, probably using a virtual data repository behind a portal.

The Academy of Sciences will host the March meeting in Canberra.

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