Inexpensive aerial photogrammetry for studies of whales and

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TitleInexpensive aerial photogrammetry for studies of whales and large marine animalsAbstractWe describe a simple system enabling accurate measurement of swimming marine mammals and other large vertebrates from low-altitude single-frame photogrammetry via inexpensive modifications to a 'prosumer' unmanned aerial vehicle (UAV) equipped with gimballed micro4/3 camera and 25 mm lens. Image scale is established via an independently powered LIDAR/GPS data-logging system recording altitude and GPS location at 1 Hz. Photogrammetric calibration of the camera and lens allowed distortion parameters to be rigorously accounted for during image analysis, via a custom-programmed Graphical User Interface (GUI) running in MATLAB. The datalogger, camera calibration methods and measurement software are adaptable to a wide range of UAV platforms. Mean LIDAR accuracy, measured from 10 bridges 9-39 m above water, was 99.9%. We conducted 136 flights in New Zealand's subantarctic Auckland Islands to measure southern right whales. Mean lengths of 10 individual whales, each photographed between 7 and 15 times, had CVs (SD/mean) ranging from 0.5 to 1.8% (mean = 1.2%). Repeated measurements of a floating reference target showed a mean error of c.1%. Our system is relatively inexpensive, easily put together, produces accurate, repeatable measurements from single vertical images, and hence is applicable to a wide range of ecological questions in marine and terrestrial habitats. © 2017 Dawson, Bowman, Leunissen and Sirguey.

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1st AuthorDawson, S. AuthorDawson, S.Bowman, M.Leunissen, E.Sirguey, P.Year2017JournalFrontiers in Marine ScienceVolume4NumberNOVDOI10.3389/fmars.2017.00366URLhttps://www.scopus.com/inward/recor.....1214509e4bec6219979d90900PublisherFrontiers Media S. AAuthor KeywordsAerialLIDARPhotogrammetryUAVWhale

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CitationDawson, S., Bowman, M., Leunissen, E. and Sirguey, P. (2017). Inexpensive aerial photogrammetry for studies of whales and large marine animals. Frontiers in Marine Science, 4(NOV)