Remote sensing researchers and UAV engineers surveying Ningaloo Reef. Photo: QUT REF.
Coral reefs around the world are facing a growing threat from expanding human developments, climate change and global sea level rise. To better understand how ecosystems like this respond to such changes, new technology has been launched to combine the advanced insights of remote sensing and the accessibility now offered by drones.
Remote sensing researchers from the Queensland University of Technology (QUT) are pioneering the use of new miniaturised hyperspectral cameras to monitor the health of Australian landscapes in more detail than ever before. The system was recently trialled at Western Australia’s Nigaloo reef, one the largest fringing coral reefs in the world.
Project leader Associate Professor Felipe Gonzalez said his team was among the first in the world to obtain aerial hyperspectral imagery of a coral reef in such high resolution. The data-gathering mission is expected to help inform future research not only for reefs but also for ecosystems of all types at sea and on land.
The hyperspectral UAV system surveyed approximately 40ha of Ningaloo Reef in 30 minutes at a flight height of 100m. Photo: QUT REF
Professor Gonzalez said new lightweight hyperspectral cameras would open many possibilities for reef monitoring. On the other side of the continent, NASA’s Coral Reef Airborne Laboratory (CORAL) mission is currently conducting hyperspectral mapping of the Great Barrier Reef at high altitude with manned aircraft. However, unmanned craft offer a new level of accessibility.
“UAVs are a cost-effective sensor platform and a great complementary tool to existing satellite, manned aircraft and underwater surveys,” Professor Gonzalez said.
“Large-scale, high-altitude surveys of the Ningaloo and Great Barrier reefs may lack the resolution necessary to identify individual corals, so this is the niche for low-altitude UAV surveys.”
Normal cameras record images only in three bands of the visible spectrum, red, green and blue. By comparison, the hyperspectral camera’s 270 bands in the visible and near-infrared portions of the spectrum provide far more detail and insights than previously possible.
QUT researcher engineer Dr Dmitry Bratanov said the resolution and hyperspectral data acquired by such methods opens up a new form of environmental monitoring.
“This provides us with a spatial resolution of approximately 15cm per pixel – more than enough detail to detect and monitor individual coral species” Mr Bratanov said.
“The really special thing about the hyperspectral camera is that it takes images across 270 slices of the spectrum. This huge amount of information allows for the classification of coral species, sand and algae based on their unique spectral signatures.”
Using data collected by engineers in the IFE’s Research Engineering Facility (REF), lead researcher Professor Gonzalez and his team are developing revolutionary software to quickly analyse the airborne hyperspectral information from Ningaloo reef and are also working on hyperspectral camera unit into an underwater housing for marine robots.
The resulting methods are expected to be applicable for a wide range of other environmental purposes, including detecting invasive plants and diseases in wheat crops.
Professor Gonzalez said the hyperspectral signatures act very much like fingerprints.
“We’re building artificial intelligence algorithms that can automatically recognise and classify these unique signatures – the hyperspectral equivalent of a police ‘fingerprint database’, Professor Gonzalez said.
“This database will become increasing valuable to all environmental researchers into the future.”
“The CORAL system provides a resolution of 7.5m per pixel compared to QUT’s UAV system at 15cm per pixel, and our manned aircraft fitted with a hyperspectral camera which captures data at 35cm per pixel at 230 m off the ground,” Professor Gonzalez said.
