Fig. 3. Frame from a video sequence at 50 frames s^–1 of a steppe eagle's tail taken by an onboard wireless video camera. The graphs plot the measured tail bank angle and angle of attack as functions of time with no filtering applied. Tail bank angle () is extracted from the angle of the trailing edge, as shown by the construction lines on the image. Tail pitch angle () is extracted by measuring the deviation of the trailing edge from its average position perpendicular to the line AB at the point A, and making use of the known distance of the camera to the base of the tail. Tail spread angle is not shown, but can also be determined from these data, giving 3 measurable kinematic degrees of freedom for the tail.