Multiple UWB Range Assisted GPS RTK in Hostile Environments

Glenn MacGougan, Kyle O’Keefe, David S. Chiu

Abstract:	Ultra-wideband (UWB) ranging radios are an emerging technology that offers precise, short range ranging in areas where GPS signals are degraded. In this paper, UWB is investigated as a method to augment carrierphase GPS positioning in an urban canyon. The ranging accuracy of the UWB ranging radio system is first evaluated and a significant scale factor error is discovered. This is explained in terms of a geometric walk effect that results from the energy detection method used by the UWB radios to estimate the time-of-arrival of the UWB signal. An augmented carrier-phase RTK float filter is then developed that can be augmented with UWB range measurements obtained using UWB reference stations that are pre-surveyed using GPS. The rover user then makes both GPS and UWB observations. The float position and double-difference ambiguity solutions are then compared with and without additional UWB ranges. The addition of UWB ranges to the solution shows significant improvement in terms of float solution convergence, both in the position and ambiguity domains. Ambiguities are resolved using the LAMBDA method and validated with a ratio test. The UWB augmented solution shows a large improvement in terms of ratio and time to first fix, though the actual precision of the fixed solution remains unchanged. The test is then repeated with a higher elevation mask and in the this case the GPS only solution is unable to resolve correct ambiguities at all while the UWB augmented solution remains accurate by usual RTK standards.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	3020 - 3035
Cite this article:	MacGougan, Glenn, O’Keefe, Kyle, Chiu, David S., "Multiple UWB Range Assisted GPS RTK in Hostile Environments," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 3020-3035.
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