New and Improved Ways to Estimate Propulsive Body Acceleration of Marine Mammals
Tags incorporating accelerometers have provided powerful tools for understanding the behavioral kinematics of marine mammals. The accelerometer signal has been used to estimate energy expenditure, commonly with the ODBA metric (Overall Dynamic Body Acceleration). However, with such tags the linear accelerations of an animal cannot be clearly disambiguated from angular velocities owing to the dominance of the gravitational acceleration signal. Incorporating a gyroscope overcomes this constraint. We propose two new metrics with associated methods to take advantage of combined 3- axis gyroscope and accelerometer data: the Estimated Linear Body Acceleration metric (ELBA) which estimates overall dynamic accelerations, and Estimated Propulsive Body Acceleration (EPBA) which estimates body accelerations related to propulsion. We evaluated the new metrics using trained Steller sea lions (Eumetopias jubatus) equipped with Loggerhead Instrument's OpenTags. The sea lions swam alongside a boat at controlled speeds ranging from 4 to 10 kph. At each speed, we computed ELBA, EPBA, ODBA and VeODBA (a variant on ODBA). The results show that the new measures - ELBA, EPBA - are significantly better predictors of speed. In addition, EPBA more closely approximates accelerations expected due to drag.
Journal or Conference Title
International Bio-Logging Science Symposium (BLS5)
Sep 22 - Sep 27, 2014
C. Ware, Trites, A., and Rosen, D., “New and Improved Ways to Estimate Propulsive Body Acceleration of Marine Mammals”. 2014.