Performance and Accuracy of Lightweight and Low-Cost GPS Data Loggers According to Antenna Positions, Fix Intervals, Habitats and Animal Movements

Abstract

Recently developed low-cost Global Positioning System (GPS) data loggers are promising tools for wildlife research because of their affordability for low-budget projects and ability to simultaneously track a greater number of individuals compared with expensive built-in wildlife GPS. However, the reliability of these devices must be carefully examined because they were not developed to track wildlife. This study aimed to assess the performance and accuracy of commercially available GPS data loggers for the first time using the same methods applied to test built-in wildlife GPS. The effects of antenna position, fix interval and habitat on the fix-success rate (FSR) and location error (LE) of CatLog data loggers were investigated in stationary tests, whereas the effects of animal movements on these errors were investigated in motion tests. The units operated well and presented consistent performance and accuracy over time in stationary tests, and the FSR was good for all antenna positions and fix intervals. However, the LE was affected by the GPS antenna and fix interval. Furthermore, completely or partially obstructed habitats reduced the FSR by up to 80% in households and increased the LE. Movement across habitats had no effect on the FSR, whereas forest habitat influenced the LE. Finally, the mean FSR (0.90 ± 0.26) and LE (15.4 ± 10.1 m) values from low-cost GPS data loggers were comparable to those of built-in wildlife GPS collars (71.6% of fixes with LE < 10 m for motion tests), thus confirming their suitability for use in wildlife studies.

Fig 1. Motion controlled tests.

Locations recorded by the Garmin control device (small dark dot) and two CatLog data loggers (large green and blue dots) with a fix interval set to 1 min along the path centered on Briquenay. Red points represent starting and ending points.

Fig 2. Systematic error.

Location errors from 39 GPS CatLog data loggers relative to the National Geodetic Survey coordinates obtained of (a) 700–2300 fixes per unit under antenna positions (up or down) and fix intervals (program A, program B or program C) in an open habitat and (b) 250–2300 fixes per unit under different habitats with fixed conditions. Ellipses represent 95% confidence areas and centroids represent the average location error.