Sea floor survey from the sky

The Dash-8 aircraft flies over Macquarie Islandís isthmus as it conducts a Laser Airborne Depth Sounder (LADS) survey.
The Dash-8 aircraft flies over Macquarie Islandís isthmus as it conducts a Laser Airborne Depth Sounder (LADS) survey. (Photo: Vicki Heinrich)
The Dash 8 on the runway at Invercargill with the nine person survey team standing beside.A Dash 8 aircraft against blue sky.View of the shallow coastal waters off Macquarie Island from the LADS survey flight.

Airborne surveyors are helping to map the shallow sea floor adjacent to Macquarie Island research station, in preparation for the arrival of Australia’s new icebreaker RSV Nuyina.

The Royal Australian Navy’s Laser Airborne Depth Sounder (LADS) team spent five days last month conducting 90 minute surveys in a Dash 8 aircraft, over the shallow waters either side of the island’s isthmus.

Project coordinator, Ursula Harris, from the Australian Antarctic Division, said the LADS team flew at various heights between 3000 and 1200 feet (914-366 metres), over the northern end of the island.

“We already have good navigation charts for the island where the Aurora Australis and tourist ships operate, but we need to improve them as the Nuyina has a deeper draft,” Ms Harris said.

“This work will contribute to a contour map of the shallow waters, with depth soundings and rock features.”

The airborne survey is an efficient way to collect a large amount of data, as the flights can survey more than 50 square kilometres an hour.

Coordinator of the LADS Flight, Lieutenant Commander Mark Matthews, said the laser has a scan width of up to 598 metres and can record depths (bathymetry) of up to 80 metres in clear water.

“We conducted five sorties from Invercargill in New Zealand to Macquarie Island, with each survey lasting about 90 minutes within a total flight time of seven hours,” LCDR Matthews said.

“The LADS system is particularly suited to coastal and reef areas where it may be dangerous for survey ships to operate, and we can cover vast areas more efficiently than surface-based vessels.”

The LADS team worked closely with the Macquarie Island Station Leader and Parks and Wildlife rangers on the island, to ensure there was no disturbance to wildlife.

“We had rangers monitoring penguins and seals as the aircraft flew its survey lines, to call a halt to operations if there was any disturbance, but there was none,” Ms Harris said.

A team of three Navy hydrographers and an Army surveyor are currently on the island to ground-truth and validate some of the LADS data in very shallow waters off The Isthmus.

The team is also surveying beaches used to land people and cargo during resupply, and completing a terrestrial survey to assist with the design and build of a new Macquarie Island research station.

“Altogether, the data will allow us to produce a continuous model of The Isthmus’s terrain, from the land into the shallow waters, for the new station’s project team and building contractors, as well as allowing us to update our navigation charts further out to sea,” Ms Harris said.

The Australian Antarctic Division has been conducting survey work with the Navy and Geoscience Australia in the waters off Casey, Davis and Mawson research stations in Antarctica to improve navigational charts and understand the glaciological history of the regions.