Design of efficient navigation message format for UAV pseudolite navigation system

This paper presents an efficient method of designing an appropriate navigation message format for an airborne pseudolite navigation system using unmanned aerial vehicle (UAV) platforms. We briefly describe the concept of the UAV pseudolite system, which can be used as a GPS augmentation system or a local navigation system. Because the motion of UAVs is very variable, a special format is necessary for UAV navigation messages. Our approach is based on specialized message formats for each motion of the UAV, including both line and circle tracking, and the separation of nominal values and deviations. It can reduce the total size of the message and diminish the latency problem. The space saved by the smaller messages can be used for the other useful messages. To verify the proposed message format, we analyzed logged data from UAV flight tests. Although the UAV we used is an experimental vehicle with a limited control system using a single antenna GPS receiver, the overall performance was consistent with current satellite-based systems. The proposed message formats and the related design method will be capable of extension for an airship-based system or a balloon-based system.