Drones for
reef surveys
As in many fields
of science, re-
searchers are de-
veloping ways to
investigate the
condition of coral
reefs using drone
technology.
Drones have
been frequently
used to take pho-
tos and video in
military and law
enforcement ap-
plications, but the
use of these unmanned aerial vehicles for research pur-
poses is still in its infancy. An international team of sci-
entists headed by Elisa Casella of the Leibniz Center for
Marine Tropical Research (ZMT) has developed a way to
use them to investigate the condition of shallow marine
tracts, as reported in the journal Coral Reefs.
Thanks to small size, improved control, and falling
prices, many disciplines can now benefit from drones.
They enable entirely new methods of ecological research
and environmental protection. For example, they are al-
ready being used to map remote areas and agricultural
lands and to inventory threatened animal species. So far,
they have not been used extensively to explore marine
ecosystems, but a drone can provide an overview of a
coral reef and its structural characteristics that it would
take divers days of collecting data to accomplish.
In Moorea, an island in the South Pacific that be-
longs to French Polynesia, researchers from the ZMT, in
cooperation with colleagues from the Centre de Recher-
ches Insulaires et Observatoire de l’Environnement, test-
ed their method on a shallow-water reef. They launched
a quadcopter equipped with a small camera from a boat.
From an altitude of about 100 feet (30 m), the drone
overflew the ecosystem; every two seconds the camera
shot images from different angles. Based on 300 record-
ings, the researchers assembled a 3-D reconstruction of
the coral reef using custom software.
“The detail accuracy of the images is amazing,” said
Casella. “We can even distinguish between different
coral types. Satellite images, on the other hand, have a
much lower resolution.” Challenges like strong light re-
flections and optical distortions that occur in the water-
to-air transition were overcome. “We went to the reef on
windless days and took the pictures at low sun angles,”
said Casella.
“This is a very elegant and time-saving method to get
an impression of the condition and structure of a coralLaunching
the drone
over the
reef in
Moorea.E. CASELLA, LEIBNIZ CENTER FOR MARINE TROPICAL RESEARCH