Decision rules for determining terrestrial movement and the consequences for filtering high-resolution global positioning system tracks: a case study using the African lion ( Panthera leo )

Richard M. Gunner, Rory P. Wilson, Mark D. Holton, Phil Hopkins, Stephen H. Bell, Nikki J. Marks, Nigel C. Bennett, Sam Ferreira, Danny Govender, Pauli Viljoen, Angela Bruns, O. Louis van Schalkwyk, Mads F. Bertelsen, Carlos M. Duarte, Martin C. van Rooyen, Craig J. Tambling, Aoife Göppert, Delmar Diesel, D. Michael Scantlebury

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Abstract

The combined use of global positioning system (GPS) technology and motion sensors within the discipline of movement ecology has increased over recent years. This is particularly the case for instrumented wildlife, with many studies now opting to record parameters at high (infra-second) sampling frequencies. However, the detail with which GPS loggers can elucidate fine-scale movement depends on the precision and accuracy of fixes, with accuracy being affected by signal reception. We hypothesized that animal behaviour was the main factor affecting fix inaccuracy, with inherent GPS positional noise (jitter) being most apparent during GPS fixes for non-moving locations, thereby producing disproportionate error during rest periods. A movement-verified filtering (MVF) protocol was constructed to compare GPS-derived speed data with dynamic body acceleration, to provide a computationally quick method for identifying genuine travelling movement. This method was tested on 11 free-ranging lions ( Panthera leo ) fitted with collar-mounted GPS units and tri-axial motion sensors recording at 1 and 40 Hz, respectively. The findings support the hypothesis and show that distance moved estimates were, on average, overestimated by greater than 80% prior to GPS screening. We present the conceptual and mathematical protocols for screening fix inaccuracy within high-resolution GPS datasets and demonstrate the importance that MVF has for avoiding inaccurate and biased estimates of movement.
Original languageEnglish
Article number20210692
JournalJOURNAL OF THE ROYAL SOCIETY INTERFACE
Volume19
Early online date19 Jan 2022
DOIs
Publication statusEarly online date - 19 Jan 2022

Keywords

  • Life Sciences–Physics interface
  • Research articles
  • acceleration
  • animal behaviour
  • data filtering
  • global positioning system
  • highresolution
  • terrestrial movement

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