3D tracking of animals in the field, using rotational stereo videography

Abstract

We describe a method for tracking the path of animals in the field, based on stereo videography and aiming-angle measurements, combined in a single, rotational device. In open environments, this technique has the potential to extract multiple 3D positions per second, with a spatial uncertainty of <1 m (rms) within 300 m of the observer, and <0.1 m (rms) within 100 m of the observer, in all directions. The tracking device is transportable and operated by a single observer, and does not involve any animal tagging. As a video of the moving animal is recorded, track data can easily be completed with behavioural data. We present a prototype device based on accessible components that achieves about 70% of the theoretical maximal range. We show examples of bird ground and flight tracks, and discuss the strengths and limits of the method, compared with existing fine-scale (e.g. fixed-camera stereo videography) and largescale tracking methods (e.g. GPS tracking).

A call for viewshed ecology: Advancing our understanding of the ecology of information through viewshed analysis

“…In this respect, the increased availability of unmanned aerial vehicles offers ecologists an unprecedented opportunity to obtain LiDAR data at a user‐defined scale and point density (Anderson & Gaston, ; Strandburg‐Peshkin et al., ). In addition, technical advances in animal tracking (Cagnacci, Boitani, Powell, & Boyce, ; De Margerie, Simonneau, Caudal, Houdelier, & Lumineau, ; Kays, Crofoot, Jetz, & Wikelski, ; Shipley, Kapoor, Dreelin, & Winkler, ) has drastically increased the spatial resolution (also in 3D) of location data which means that the spatial precision offered by LiDAR can increasingly be utilized to its full potential for viewshed ecology.…”

Gliding for a free lunch: biomechanics of foraging flight in common swifts (Apus apus)

“…The RSV method natively produces position measurements in a spherical coordinate system Θ, Φ, Ρ (i.e. azimuthal angle, elevation angle and radius), with a measurement uncertainty for Ρ that increases proportional to Ρ 2 and is a fixed property of the device for Θ and Φ (de Margerie et al, 2015). The cumulative outcome of these uncertainties in 3D Cartesian space is a random position uncertainty attaining 0.2, 0.8 and 1.8 m at 100, 200 and 300 m, respectively.…”

“…Here, we quantified swift flight trajectories by rotational stereo videography (RSV), which uses a camera and telephoto lens with a set of mirrors to combine views from two vantage points into one image, all mounted on an instrumented pivot to track individual birds during flight (de Margerie et al, 2015). Application of this and other videographic methods enables measurement of field flight biomechanics with high spatial (centimetre-metre scale) and temporal (5-100 Hz) resolution, even for species where use of an on-board satellite-based positioning package is currently infeasible because of weight or other restrictions.…”

Why study cognition in the wild (and how to test it)?

“…One application of this technology is the ability to track the movements and paths of animals in 3D, based on the view of multiple calibrated cameras. Although thus far the use of this technology in animal behavior research has mostly been restricted to the laboratory (but see Clark, ; de Margerie et al, ; Thierault et al, ), it has been used recently to track the flight paths of hummingbirds as they searched for a previously visited flower (Pritchard et al, 2016b, Fig. ).…”