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October 22, 2019

Photogrammetry explained: a non-invasive way to obtain marine mammal measurements

Thanks to your support of generous donations and Pacific Whale Foundation memberships, the Research Department was able to purchase a state-of-the-art laser photogrammetry system to add to our research tool kit! Photogrammetry is a laser system mounted to a camera that projects two laser dots, set at a fixed distance apart, onto an animal’s dorsal fin or body. Since we know the distance between the lasers, the two dots act as a ruler projected right onto the animal, allowing us to calculate measurements of animals from our photos. In the field, we take photo-ID of an animal’s dorsal fin to identify the individual dolphin, and when an animal is swimming parallel and close to our research vessel, we are more likely to get a photo with the lasers projected onto its body. Along with getting measurements of dolphins, the new photogrammetry setup gives our researchers a great workout. The camera and mounted photogrammetry system weigh about 10 pounds!  
Example of a successful photo of a pilot whale with two lasers projected onto it’s dorsal fin
Photogrammetry system mounted to the camera
Calibrating the set distance between the two lasers in the office
Taking photo-ID in the field with the photogrammetry camera

After the field research is done, the post-field-work processing begins back in the lab. For each individual, we take the best quality image with both lasers visible and use a program called ImageJ to measure the dorsal fin base width, height, surface area, and body length index. From these measurements, we will be able to estimate the age and size of individual animals. Repeated measurements of the same animals can then also be used to determine the health and age demographics of the populations we are studying.

Bottlenose dolphin surface area measurement
Bottlenose dolphin dorsal base width measurement
Bottlenose dolphin dorsal base width measurement
Bottlenose dolphin body length index measurement

So far, we have obtained photogrammetry images of 5 species of dolphin: bottlenose dolphins, spinner dolphins, spotted dolphins, pilot whales, and false killer whales.  We have collected images of both sexes and varying age classes for all the species. Pacific Whale Foundation is at the forefront of using emergent technologies to conduct our work and evolve the field of marine mammal research. New technology in combination with traditional research methods allows us to collect more robust and meaningful data. This new tool will give us the ability to learn much more about the cetaceans we are studying in Maui Nui. We look forward to continuing this work and sharing our exciting results.