Abstract:
BACKGROUND: Fine-scale data on animal position are increasingly enabling us to understand the details of animal
movement ecology and dead-reckoning, a technique integrating motion sensor-derived information on heading and
speed, can be used to reconstruct fine-scale movement paths at sub-second resolution, irrespective of the environment.
On its own however, the dead-reckoning process is prone to cumulative errors, so that position estimates
quickly become uncoupled from true location. Periodic ground-truthing with aligned location data (e.g., from global
positioning technology) can correct for this drift between Verified Positions (VPs). We present step-by-step instructions
for implementing Verified Position Correction (VPC) dead-reckoning in R using the tilt-compensated compass
method, accompanied by the mathematical protocols underlying the code and improvements and extensions of this
technique to reduce the trade-off between VPC rate and dead-reckoning accuracy. These protocols are all built into
a user-friendly, fully annotated VPC dead-reckoning R function; Gundog.Tracks, with multi-functionality to reconstruct
animal movement paths across terrestrial, aquatic, and aerial systems, provided within the Additional file 4 as well as
online (GitHub).
RESULTS: The Gundog.Tracks function is demonstrated on three contrasting model species (the African lion Panthera
leo, the Magellanic penguin Spheniscus magellanicus, and the Imperial cormorant Leucocarbo atriceps) moving on
land, in water and in air. We show the effect of uncorrected errors in speed estimations, heading inaccuracies and
infrequent VPC rate and demonstrate how these issues can be addressed.
CONCLUSIONS: The function provided will allow anyone familiar with R to dead-reckon animal tracks readily and accurately,
as the key complex issues are dealt with by Gundog.Tracks. This will help the community to consider and implement
a valuable, but often overlooked method of reconstructing high-resolution animal movement paths across
diverse species and systems without requiring a bespoke application.
