Flight-Test Evaluation of Navigation Information in Wide-Field Optical Flow

Wide-field optical flow information can benefit the navigation of small or micro unmanned aerial vehicles in GPS-degraded/denied environments, inspired by the study of insect/bird flights. This paper focuses on a flight-test evaluation of navigation information in wide-field optical flow, using flight data collected by a wide-angle camera installed on a fixed-wing unmanned aerial vehicle at altitudes ranging from 30 to 183m above the ground. A comprehensive evaluation methodology is proposed for the comparison between optical flows computed from videos and the reference motion fields determined from conventional navigation sensors including GPS, a laser range finder, and inertial sensors. Seven sets of unmanned aerial vehicle flight data including a total of approximately 72,000 image frames are used for both full-flight temporal evaluation and representative interframe spatial evaluation of wide-field optical flow information for unmanned aerial vehicle navigation purposes. The evaluation results showed a good match between vision-derived optical flows and reference motion fields from conventional navigation sensors. Finally, one benchmark data set is shared at the authors' website for open access from the research community.