With the Belugas… and Their Waist Measurements!
For the past several years, scientists have been using drones to study wildlife in their natural environment. Besides the esthetic appeal of the images they provide, drones provide a different perspective than what we are accustomed to from ships or land-based observation sites. This new point of view opens the door to a multitude of exploration possibilities. The project we are launching aims to assess the health status of belugas using “measurements” derived from aerial photos taken by drones. This technique is called photogrammetry.
GREMM’s lead technician Michel Moisan has once again demonstrated his creativity by equipping a standard drone with a number of complementary gadgets to meet this new challenge. This type of drone is already used in engineering to measure all kinds of buildings and calculate volumes. However, drone positions are based on fixed land-based reference points, which we cannot use, as we are constantly travelling with the belugas aboard a boat. It was therefore necessary to adapt, so Michel equipped our flying spy with a lidar (acronym for “light detection and ranging”) that measures at 1-second intervals the height of the drone above the water surface by means of a light beam that the lidar emits and receives. Once the drone is in flight, a photo is taken of a plate of known dimensions on board the boat that serves as a reference to adjust the lidar measurements as needed. Then we can begin taking photos of the belugas while constantly remaining at the same height at which the calibration photo was taken.
Although this technique is already used in other cetacean species – including killer whales and right whales – it is still in its infancy in belugas. In addition to taking carefully-timed pictures of belugas with a drone while positioning the camera directly above them, we also simultaneously strive to shoot photos from the boat of the same group the drone is hovering over while staying parallel to the animals, as per our photo-ID protocol. That is the real challenge of this project, combining photogrammetry with photo-identification. Why combine these two technologies? In order to be able to recognize drone-photographed individuals and thus be able to track the evolution of their condition over time, whether during a single season or over the course of several years. In short, our new objective is to establish a health chart of all St. Lawrence belugas featured in our photo-identification catalogue.
The first few weeks served as a testing period and required a few adjustments, but in the end we got into a groove and managed to overcome this new challenge. And we’ll certainly face new challenges when it comes time to analyze the data! To be continued!
Preliminary identifications of the week: