High Precision RTK Positioning under Canopy Environments

X. Luo, F. Hurter, B. Richter, M. Carrera, A. Cole, F. Takac

Abstract:	GNSS RTK positioning is rarely subject to ideal open sky conditions and is now increasingly used in difficult environments such as urban canyons and tree canopy. When performing RTK surveys under tree cover, GNSS signals are blocked, attenuated and reflected, resulting in cycle slips, losses of lock and multipath effects. Under these circumstances, an accurate and reliable RTK solution within a short time represents an extremely challenging task and requires robust signal tracking techniques and sophisticated positioning algorithms. The objective of this paper is to present the results of new approaches enabling high precision RTK positioning in canopy environments. In terms of signal tracking performance, phase lock loop parameters and acquisition/reacquisition thresholds are optimized to increase the availability of GNSS measurements under tree canopy. The positioning algorithm is then tuned for reliable cycle slip detection and the optimal use of carrier-phase, code and Doppler observations to improve ambiguity success rate, positioning quality and time to fix. The results of RTK positioning under canopy are analyzed in both the measurement and position domains. The measurement domain analysis focuses on the signal tracking quality, whereas the position domain analysis considers availability, accuracy, reliability and time to fix. Regarding the RTK fixed solutions in static mode, centimeter level positioning accuracy can be achieved with fast time to fix. In kinematic mode, the availability of high precision RTK positions strongly depends on the degree of canopy, where unbiased height estimates are obtainable in medium and heavy canopy with centimeter-level accuracy. Based on the results presented in this paper, the Leica Viva GNSS technologies have been optimized to deliver maximum RTK performance in difficult environments.
Published in:	Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015) September 14 - 18, 2015 Tampa Convention Center Tampa, Florida
Pages:	569 - 580
Cite this article:	Luo, X., Hurter, F., Richter, B., Carrera, M., Cole, A., Takac, F., "High Precision RTK Positioning under Canopy Environments," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 569-580.
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