Three-dimensional kinematics

Pigeon wing and body movements were tracked using a high speed (200 Hz) 3-d motion analysis system (Motion Analysis Corp.) designed for human kinematics. The system uses cameras that produce and collect the infrared light reflected back from markers on the bird. When calibrated, the cameras view objects in a three-dimensional coordinate space. The coordinates for the objects travelling through that space are recorded, and from these coordinates, the kinematic parameters of interest are calculated.

The markers were placed on the bird as to allow calculation of 'absolute' body and wing position, as well as wing flexion at the wrist. In addition, the three markers on the bird's back created a local three-dimensional coordinate system, from which the movement of the wings relative to the body could be determined. Below are illustrations of the position of the reflective markers, and the method of calculating angle of attack (a).

Pronation angle (d) and downstroke angle (l). Wing speed was also derived from local coordinates of the wing at position n and n+1 over time (1/200 s, or 5 ms).