Resolving issues of imprecise and habitat-biased locations in ecological analyses using GPS telemetry data

Abstract

Global positioning system (GPS) technologies collect unprecedented volumes of animal location data, providing ever greater insight into animal behaviour. Despite a certain degree of inherent imprecision and bias in GPS locations, little synthesis regarding the predominant causes of these errors, their implications for ecological analysis or solutions exists. Terrestrial deployments report 37 per cent or less non-random data loss and location precision 30 m or less on average, with canopy closure having the predominant effect, and animal behaviour interacting with local habitat conditions to affect errors in unpredictable ways. Home-range estimates appear generally robust to contemporary levels of location imprecision and bias, whereas movement paths and inferences of habitat selection may readily become misleading. There is a critical need for greater understanding of the additive or compounding effects of location imprecision, fix-rate bias, and, in the case of resource selection, map error on ecological insights. Technological advances will help, but at present analysts have a suite of ad hoc statistical corrections and modelling approaches available-tools that vary greatly in analytical complexity and utility. The success of these solutions depends critically on understanding the error-inducing mechanisms, and the biggest gap in our current understanding involves species-specific behavioural effects on GPS performance.

Global positioning system and associated technologies in animal behaviour and ecological research

“…May 2000 and permanently decommissioned in September 2007 (Kovach & Van Dyke 1998 Frair et al 2010). Commercial users will soon benefit from the addition of a second frequency (L4), to reduce ionosphere-induced errors and increase typical accuracy performance to 6 m (Sandlin et al 1995).…”

“…GPS has 24-hour coverage, with position updates available in rapid succession (one location update per second is typical). Such data can be reviewed, selected, filtered and/or statistically analysed to help ensure accuracy (Frair et al 2010). GPS often allows positions in bad weather when other approaches can be restricted.…”

“…under dense canopy, inside dens, topography; D' Eon et al 2002;Hebblewhite et al 2007;Frair et al 2010). Fix rates and location errors vary depending on environmental circumstances.…”

Wind farm construction impacts reindeer migration and movement corridors

“…The exact dates of the start and the end of the season differed between the four study years. Fix success of the GPS collars was sometimes low, *1 % of the positions were removed having high DOP-value ([10) and 2D positioning (Frair et al 2010). The data was downloaded from the collars via the global system for mobile communications (GSM) cell phone network, at some occasions the reindeer used areas with low GSM-coverage not making data download possible.…”

First known satellite collaring of a viverrid species: preliminary performance and implications of GPS tracking Malay civets (Viverra tangalunga)

“…There is currently no standardized internal calibration value of GPS fix quality in these collars, such as a dilution of precision (DOP), a common component of most unit design. These values facilitate the development of post hoc data screening protocols in order to increase the biological relevancy of acquired GPS data (Lewis et al 2007;Frair et al 2010).…”