Geoscience Australia creates integrated land map

Geoscience Australia has released a free high-resolution national map of vegetation cover across all states and territories after two years of development.

The map is the first to be sourced and created at a national level - not just by combining map data from the various states and territories.

The agency's section leader for science and strategy within the National Earth Observation Group, Methavy Thankappan, told iTnews the map is four gigabytes in size and includes three gigabytes of trend data collected by NASA’s TERRA satellite.

“It’s the first time it has been done across all states and territories at this resolution,” Thankappan said.

“In the past when the individual states and territories tried to put together the same information, a federal agency like the current Bureau of Agriculture and Resources & Energy compiles a national [map].

"We got all kinds of artefacts along the state and territory boundaries because they have used different approaches, different information, and different nomenclature.

“You end up with a mishmash of various things that don’t look right across the jurisdictional boundaries.”

The finished product compressed a total raw data set that was closer to 140 gigabytes, he said. The data set resolves maps to 250m x 250m, which equates to one pixel in the image map.

Three scientists cleaned and processed the raw data using massively parallel compute clusters.

Some of the cleansing work involved removing satellite images where clouds hid vegetation data.

“We took the imagery and composites over 16 days and used the best imagery to allow for the cloud cover,” Thankappan said.

“We have 34 classes of land cover at present from the imagery".

Thankappan said the agency aims to update the land cover map annually but that it needs "to develop a robust technology to make it easier and faster to update the dataset in the future".

He hoped to have that technology bedded down by June next year.

It is also hoped that the resolution of the map will improve in the future.

"We're considering going from a 250m resolution to a 25m resolution as in Landsat," he said.

But that means a "big jump in data volumes and details" collected under the project, throwing up new challenges.

"We [will] need to rationalise [land cover classes]," he said.

"One of the options is to look at themes rather than land cover across the whole spectrum", he said, citing an example of water dispersion.

“That reduces the complexity of the task and makes it more useful for users that want to fund a higher resolution dataset for their private or public planning.”

The land map is available from the Geoscience Australia website or at cost of transfer from the online Geoscience Australia Sales Centre. Hard copies are available free of charge from the sales centre.

DEM models

Geoscience Australia also launched Digital Elevation Modelling (DEM) data accurate to 30m across all Australia.

"The new 30m products improve our understanding of the national topography by producing digital elevation models at more than eighty times the resolution of the current national model," project manager Hamish Anderson said.

"The new data has a vertical accuracy of plus or minus 9 metres and will be of particular value in determining areas where more intensive flood risk assessment is required."

Sections of the data are available for download of up to 400Mb at a time - a file size equivalent to grabbing elevation data for land at about a third of the size of Tasmania.

For the full national perspective on elevation, the DEM data comes on a 500Gb hard drive and at a data transfer cost of around $275, according to one of its