Work

The Effects of Depth and Altitude on Image-Based Shark Size Measurements Using UAV Surveillance

Year: 2024

Type: article

Abstract: Drones are an ecological tool used increasingly in shark research over the past decade. Due to their high-resolution camera and GPS systems, they have been used to estimate the sizes of animals using drone-based photogrammetry. Previous studies have used drone altitude to measure the target size accuracy of objects at the surface; however, target depth and its interaction with altitude have not been studied. We used DJI Mavic 3 video (3960 × 2160 pixel) and images (5280 × 3960 pixel) to measure an autonomous underwater vehicle of known size traveling at six progressively deeper depths to assess how sizing accuracy from a drone at 10 m to 80 m altitude is affected. Drone altitudes below 40 m and target depths below 2 m led to an underestimation of size of 76%. We provide evidence that accounting for the drone’s altitude and the target depth can significantly increase accuracy to 5% underestimation or less. Methods described in this study can be used to measure free-swimming, submerged shark size with accuracy that rivals hand-measuring methods.

Source: Drones

DOI: 10.3390/drones8100547

Authors: Patrick T. Rex, Kevin J. Abbott, Rebecca E. Prezgay, Christopher G. Lowe

Institution: California State University, Long Beach

Language: English

Topic: Ichthyology and Marine Biology

Subfield: Nature and Landscape Conservation

Field: Environmental Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,955

Funder: State of California