Abstract
A method is described that allows one to record and reconstruct three-dimensional trajectories. A scene is filmed with two synchronized 16 mm cameras. The orientation of the cameras relative to an external reference system can be chosen arbitrarily because it is subsequently determined by software from the image coordinates of a test pattern on the two films. The orientation parameters for each camera are then used to reconstruct a three-dimensional scene from the two-dimensional image coordinates on the two films. This method makes a variety of animal behaviours accessible to quantitative analysis.