The accuracy of Fastloc‐<scp>GPS</scp> locations and implications for animal tracking

Abstract

Summary Over recent years, a major breakthrough in marine animal tracking has occurred with the advent of Fastloc‐ GPS that provides highly accurate location data even for animals that only surface briefly such as sea turtles, marine mammals and penguins. We assessed the accuracy of Fastloc‐ GPS locations using fixed trials of tags in which &gt;45 000 locations were obtained. Procedures for determining the speed of travel and heading were developed by simulating tracks and then adding Fastloc‐ GPS location errors. The levels of detail achievable for speed and heading estimates were illustrated by using empirical Fastloc‐ GPS data for a green turtle ( Chelonia mydas , Linnaeus, 1758) travelling over 3000 km across the Indian Ocean. The accuracy of Fastloc‐ GPS locations varied as a function of the number of GPS satellites used in the location calculation. For example, when Fastloc‐ GPS locations were calculated using 4 GPS satellites, 50% of locations were within 36 m and 95% within 724 m of the true position. These values improved to 18 and 70 m, respectively, when 6 satellites were used. Simulations indicated that for animals travelling around 2·5 km h −1 (e.g. turtles, penguins and seals) and depending on the number of satellites used in the location calculation, robust speed and heading estimates would usually be obtained for locations only 1–6 h apart. Fastloc‐ GPS accuracy is several orders of magnitude better that conventional Argos tracking or light‐based geolocation and consequently will allow new insights into small‐scale movement patterns of marine animals.