Proposal of Navigation Message Format for UAV Pseudolite Navigation System

Doyoon Kim, Youngsun Yun, Byungwoon Park, Sanghyo Lee, Am Cho, Jihoon Kim and Changdon Kee

Abstract:	When using a radio navigation system such as GNSS, knowing the exact position of signal source is the most important part. It affects directly to the accuracy of user positioning. The motions of the UAV are very variable so that it is more difficult to predict its trajectory than for the satellite system. However, continuous monitoring and control of the UAV can reduce this problem. In this paper, we propose efficient design methods for navigation messages with specialized formats for each state of motion and we separate these into nominal values and deviations. This can reduce the total size of message and reduce the latency problem. The space saved by the reduced size of messages can be used for broadcasting other useful messages, including almanac, augmentation, or intelligence. To verify the performance of the proposed message format, we analyzed the data logged in real-time flight tests of the UAV. Although we used an experimental UAV operating in limited conditions, the performance of the ephemeris errors is comparable with satellite-based systems. The root-mean-square of range error is bounded at 3 m and the maximum is less than 5 m with 3 s latency. When limiting the maximum range error to 3 m, the specialized format for circular motion showed approximately 1.6 times the duration of the nonspecialized format. The results in this paper can be improved considerably with fully equipped commercial UAVs. Based on the proposed navigation messages and the design scheme, it may be possible to design other specialized message formats for an airship-based system or a balloon-based system. Even if the specification of UAV or the coverage requirements are changed, the basic design scheme proposed in this paper can be applied.
Published in:	Proceedings of the 2007 National Technical Meeting of The Institute of Navigation January 22 - 24, 2007 The Catamaran Resort Hotel San Diego, CA
Pages:	1128 - 1136
Cite this article:	Kim, Doyoon, Yun, Youngsun, Park, Byungwoon, Lee, Sanghyo, Cho, Am, Kim, Jihoon, Kee, Changdon, "Proposal of Navigation Message Format for UAV Pseudolite Navigation System," Proceedings of the 2007 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2007, pp. 1128-1136.
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