Latency Compensation by Compact RTK Under Harsh Communication Environment of Land Transportation

Byungwoon Park, Donghwan Yoon, Junesol Song, Changdon Kee

Abstract:	MT(Message Type) 1004 of RTCM v3.1 is generally used as the correction message for RTK. The message mainly consists of pseudorange and carrier-phase measurement, and the observables include the distance from the satellite to the RS (Reference Station) and clock biases in receiver and satellite. Value of the terms changes so fast that the message should be transmitted as soon as possible to keep the rover’s accurate position robustly. Moreover, its unlinear variation is hard to predict, so even several seconds makes extrapolation error close to the wavelength. On the other hand, Compact RTK technique is recently proposed to implement RTK in an extremely low rate data-link, and can be a good method to compensate the time-latency and to solve the data cut-off problem in land transportation. Compact RTK protocol, recently assigned in RTCM SC-104 proprietary message MT 4081, consists of PRC (Pseuodo Rance Correction) and CPC (Carrier Phase Correction) instead of code and carrier observations. These terms vary slowly and linearly, so that 500bps is large enough to keep the RTK accuracy without any degradation. To compare the latency compensation performance of MT 4081 with MT 1004, we induced 10, 15, and 30 second intentional latency to the correction repeater in a static zero-baseline test. The receiver which was fed MT 1004 cannot keep a fixed solution when it received no message for 20 second or longer. However, the other receiver which used the MT 4081 instead of MT 1004 could compensated the 30 second latency, so that its position held the fixed mode through all the test with 3.8cm(horizontal) and 6.5cm(vertical) RMS error.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	933 - 939
Cite this article:	Park, Byungwoon, Yoon, Donghwan, Song, Junesol, Kee, Changdon, "Latency Compensation by Compact RTK Under Harsh Communication Environment of Land Transportation," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 933-939.
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