Performance Evaluation of Multiple Reference Station GPS RTK for a Medium Scale Network

T.H. Diep Dao, Paul Alves, Gérard Lachapelle

Department of Geomatics Engineering, University of Calgary, Canada.

DOI:                 

Abstract

Carrier phase-based differential GPS is commonly used for high accuracy RTK positioning because it effectively reduces the effects of spatially corrected errors such as orbital and atmospheric errors. The spatially correlated error reduction is a function of the correlated errors measured by the two receivers. Carrier phase-based single reference station (SRS) positioning is capable of providing cm accuracy for static positioning and dm for kinematic positioning under normal atmospheric conditions when the inter-antenna distance is less than approximately ten kilometres. However, under highly localized atmospheric activity, and/or with a longer inter-antenna distance, the residual differential error increases and the accuracy degrades. The University of Calgary MultiRef? multiple reference station (MRS) approach uses a network of GPS reference station to model the atmospheric conditions over a geographic region to reduce correlated measurement errors. This approach uses a conditional least-squares adjustment to predict the errors in the network area. This study focuses on an evaluation of the MultiRef? approach relative to the single reference station (SRS) approach in the observation, position and ambiguity domains. Long-term and short-term convergence accuracy tests are used to assess the effectiveness of the approach. The network used for this assessment is located in Southern Alberta, Canada. This is a medium scale network with baseline lengths ranging from 30 to 60 km. The results show a minor to significant improvement of the MRS method in all domains.

Keywords

Multiple reference station GPS RTK, single reference station GPS RTK, least squares collocation, performance evaluation

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Alves P, Ahn YW and Lachapelle G (2003): The Effects of Network Geometry on Network RTK Using Simulated GPS Data, CD-ROM Proceedings of ION GPS/GNSS 03, Institute of Navigation, Portland, Oregon, USA, 11 pages.
[2]	Alves P, and Lachapelle G (2004): A Comparison of Single Reference Station, Correction-Based Multiple Reference Station and Tightly Coupled Methods using Stochastic Ionospheric Modelling, Proceedings of the International Symposium on GPS/GNSS, Sydney, Australia (6-8 December).
[3]	Alves P (2004): Development of two novel carrier phase-based methods for multiple Reference station positioning, PhD Thesis, published as Report No. 20203, Department of Geomatics Engineering, The University of Calgary.
[4]	Alves P, Lachapelle G and Cannon ME (2004): In-Receiver Multiple Reference Station RTK Solution, CD-ROM Proceedings of ION GPS/GNSS 04, Institute of Navigation, Long Beach, California, USA, 9 pages.
[5]	Dai L, Wang J., Han S. and Rizos C. (2001): A Study on GPS/GLONASS Multiple Reference Station Techniques for Precise Real-Time Carrier Phase-Based Positioning, Proceedings of ION GPS/GNSS 01, Institute of Navigation, Salt Lake City, UT, USA, pp 392-403.
[6]	Dai L, Han S, Wang J and Rizos C (2004): Comparison of Interpolation Algorithms in Network-Based GPS Techniques, Navigation, 50(4), 277 – 293.
[7]	Fortes LPS (2002): Optimising the Use of GPS Multi- Reference Stations for Kinematic Positioning, PhD Thesis, UCGE Reports Number 20158, Department of Geomatics Engineering, University of Calgary, Canada.
[8]	Gao Y, Li Z and McLellan J (1997): Carrier phase based regional area differential GPS for decimeter-level positioning and navigation, Proceedings of ION GPS-97, Institute of Navigation, Kansas City, Missouri, USA, pp 1305-1313.
[9]	Han S and Rizos C (1996): GPS Network Design and Error Mitigation for Real-Time Continuous Array Monitoring Systems, Proceedings of ION GPS-96, Institute of Navigation, Kansas City, Missouri, USA, pp 1827-1836.
[10]	Lachapelle G and Alves P (2002): Multiple Reference Station Approach: Overview and Current Research, Invited Contribution, Expert Forum. Journal of Global positioning Systems, 1(2), 133-136.
[11]	Raquet J (1998: Development of a Method for Kinematic GPS Carrier-Phase Ambiguity Resolution Using Multiple Reference Receivers, PhD Thesis, UCGE Report Number 20116, Department of Geomatics Engineering, University of Calgary, Canada.
[12]	Waypoint Consulting Inc. (2004): GrafNav/GrafNet, GrafNav Lite, GrafMov, Inertial Explorer for Window 95TM, 98TM, 2000TM, XPTM & NTTM Operating Manual,Version 7.0. Canada
[13]	Wanninger L (1995): Improved Ambiguity Resolution by Regional Di?erential Modeling of the Ionosphere, Proceedings of ION GPS-95, Institute of Navigation, Palm Springs, CA, USA, pp 55-62.
[14]	Wübbena C, Bagge A, Seeber G, Volker B, and Hankemmeier P, (1996): Reducing Distance Dependent Errors for Real -time Precise DGPS Applications by Establishing Reference Station Netwroks, Proceedings of ION GPS-96, Institute of Navigation, Kansas City, Missouri, USA, pp 1845-1852.