UWB Assisted GPS RTK in Hostile Environments

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

Abstract:	This paper presents initial results of an experiment to augment RTK GPS with an additional range from an ultra-wideband ranging radio system. The UWB radios used for this study are the Time Domain PulsON 210 development kit. The ranging accuracy of the UWB radio pair is evaluated prior to using the ranging radio to augment a short baseline RTK float solution. One test was conducted to assess UWB range accuracies and results from a prior test performed by Ebeling (2007) are reproduced here for comparison. In the first test, it was found that UWB ranges were accurate to 0.011 m, when compared to a GPS short baseline and to a range deduced from known coordinates. This is compared to a second test, performed by Ebeling (2007), that shows that UWB range accuracy is dependent on two factors: distance and visibility. UWB to UWB radio Line-of- Sight (LOS) distances of 5 m, 10 m, 15 m, 20 m, and 25 m revealed that a general linear trend existed between precision and range. RMS values ranged from 0.017 m to 0.071 m for the 5 m and 25 m scenarios, respectively. Non-Line-of-Sight (NLOS) range accuracy was evaluated by taking 5 m ranges through a door, as well as through a wall. Ebeling (2007) found 0.037 m and 0.431 m UWB RMS error values through a door and through a wall, respectively. UWB assisted RTK was assessed in two tests. In the first test two Trimble R8 GNSS receivers, along with two PulsON 210 UWB radios were deployed using co-axial phase center mounts. Once UWB ranges were added to GPS measurements, a noticeable drop in the RMS error and standard deviation of the position solution was observed. In the east direction, average RMS error dropped from 0.0543 m to 0.0261 m after the inclusion of the UWB range observations. A second UWB-GPS augmentation test was done in a suburb in Calgary to represent more typical conditions. A large tree and a structure were used to replicate signal attenuation, signal masking and multipath. Once again, results indicated that there is improvement with the addition of the UWB range. The position solution showed greater accuracy with the UWB-GPS combination over GPS alone. This is also partly reflected in the lower overall standard deviation values in the UWB augmented GPS solution. Finally, an evaluation of the Dilution of Precision (DOP) for both scenarios also demonstrates improved performance with UWB-GPS integration.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	532 - 542
Cite this article:	Chiu, David S., MacGougan, Glenn, O’Keefe, Kyle, "UWB Assisted GPS RTK in Hostile Environments," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 532-542.
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