Camera calibration for UAV ground feature localization

This paper describes a method to calibrate the geometric position and orientation of a camera mounted onto the underside of an unmanned aerial vehicle (UAV). The method takes as input multiple images captured in flight of a stationary ground feature for which GPS coordinates are known. The UAV´s location and pose during each image capture is assumed known from on-board GPS and IMU devices. The ground feature´s pixel coordinates in each image are also known (obtained using image processing or by inspection). Using these inputs, the described method uniquely determines the camera´s relative position/orientation with respect to the UAV using a nonlinear root-finding algorithm. The method represents a simple, yet effective, calibration procedure that uses information that is readily obtained from a typical UAV flight. Results from test flight experiments are presented.