Three-Dimensional Reconstruction of Animal Flight Paths and the Turning Flight of Microchiropteran Bats

Abstract

A method is presented by which a microcomputer is used to reconstruct the structure of a three-dimensional object from images obtained with a pair of non-metric cameras when the images contain the vertices of a cube as test patternand the camera-object configuration satisfies straightforward geometrical conditions. With a still camera and stroboscopic or repeating flash illumination, or with a cine camera, this method provides a simple and economic means of recording the flight path and wing movements of a flying animal accurately and reliably. Numerical methods for the further analysis of three-dimensional position data to determine velocity, acceleration, energy and curvature, and to interpolate and to correct for distortion due to inaccurate data records are described. The method is illustrated by analysis of a slow, powered turn of the bat Plecotus auritus (L.). Accurate reconstruction of the flight path permits mechanical forces and accelerations acting on the bat during the turn to be estimated: turning speed and radius in a narrow space are restricted by the bat's ability to generate sufficient lift to support the weight in nonlinear level flight.