Alcoa sees the woods for the trees

The use of remote sensing technologies is enabling Alcoa of Australia to better monitor the effectiveness of its rehabilitation efforts in the Jarrah Forest region south of Perth.

Alcoa has operated bauxite-mining projects in the area since 1963, more recently working alongside the state government to help restore the forest’s ecosystem.

While those efforts have in the past proved difficult to measure, the use of remote sensing technologies has given Alcoa a better understanding of its rehabilitation work.

Alcoa environmental improvement specialist Cameron Richardson said the business had already rehabilitated 200 square kilometres of the Jarrah Forest, with half of that area now ready for sign-off with the state government.

Mr Richardson told Business News he and the team at Alcoa had built a tree-detection model that identified a profile of individual trees rather than relying on random sampling methods.

“Existing techniques to individualise trees are very hard to apply in the Jarrah Forest because (eucalyptus) are all entwined,” he said.

“Essentially, because they’re not of a uniform shape with uniform spacing, it’s hard for the existing tree-detection models to separate them.

“It was quite novel; we were able to able to do that based on the stage of different height increments.”

Mr Richardson said the model used by Alcoa incorporated the use of several technologies, including data derived from light detection and ranging (LIDAR) imaging, which is a form of 3D modelling taken by airborne laser scanners attached to piloted, fixed-wing aircraft to capture imaging over large areas.

“As the laser pulse leaves the sensor and heads towards the ground, it intercepts with vegetation along the way,” he said.

“The laser pulse reflects back and we get elevation information.

“Because the laser pulse is 20 centimetres in diameter, portions of it can keep going towards the ground and intercept with more vegetation and eventually the ground, so we get more returns from the same pulse.

“That’s actually quite unique because it’s able to penetrate the tree canopy.”

On top of manned aircraft, Mr Richardson said Alcoa had also used unmanned aerial vehicles and remotely piloted aircraft to get photogrammetry data.

Although that data cannot construct imagery to the same detail as LIDAR imagery, he said the images it returned provided a measure for the health of individual trees

Elsewhere, Mr Richardson said Landsat satellite imagery had been used to derive vegetation indices, which had allowed Alcoa to determine the health and growth of the forest since the start of its rehabilitation efforts.

“Satellite imagery for the whole forest goes as far back as 1972,” he said.

“[With that imagery,] we can watch that restored site grow and respond to disturbance and recover.”

Mr Richardson said implementation of the technology was still early, but he was hoping Alcoa would begin using it for measuring reforestation at other sites, including in the Karri Forest area.

Beyond that, he is eager to introduce multispectral imaging currently used by The Department of Biodiversity, Conservation and Attractions, so additional information about trees not available to the human eye can be measured.

Mr Richardson said if that technology could be incorporated into the existing model, its capabilities and applications could be applied to Alcoa’s global rehabilitation efforts.

“Once the data is there and the processes are approved, there’s no reason we can’t use it everywhere and anywhere in the world,” he said.

“Starting with the Jarrah Forest is a good start with the difficulty of detecting the trees."