Adaptive Tropospheric Delay Modelling in GPS/INS/Pseudolite Integration for Airborne Surveying

Jianguo Jack Wang, Jinling Wang

School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, NSW 2052 Australia.

DOI:                 

Abstract

Integrated GPS/INS systems have been used for geo-referencing airborne surveying and mapping platforms. However, due to the limited constellation of GPS satellites and their geometric distribution, the accuracy of such integrated systems cannot meet the requirements of precise airborne surveying. This problem can be addressed by including additional GPS-like ranging signals transmitted from the ground-based pseudolites (PLs). As GPS measurement geometry could be strengthened dramatically by the PL augmentation, the accuracy and reliability of an integrated system can be improved, especially in the vertical component. Nevertheless, some modelling challenges exist in PLs augmentation. As PLs are relatively close to receivers, the unit vectors from a PL to he reference and rover receivers can be significantly different. PL tropospheric delay modelling errors cannot be effectively mitigated in a differencing procedure. Furthermore, PL signals propagate through the lower troposphere, where it is very difficult to accurately model the signal delay due to temporal and spatial variations of meteorological parameters. In this paper, an adaptive PL tropospheric delay modelling method is developed to reduce such modelling errors by estimating meteorological parameters in a model. The performance of this adaptive method isevaluated with field test data. The testing results haveshown that the PL tropospheric delay modelling error can be effectively mitigated by the proposed method.

Keywords

Pseudolite, tropospheric delay, integrated navigation, adaptive modelling, airborne surveying

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Abdullah, Q.A., Hussain, M. and Munjy, R (2002) Airborne GPS-controlled Aerial-triangulation: Theory and Pratical Concepts. ASPRS/ACSM 2002, Washington, DC.
[2]	Barltrop, K.J., Stafford, J.F. and Elrod, B.D. (1996) Local DGPS With Pseudolite Augmentation and Implementation Considerations for LAAS. In: ION (Editor), GPS, Kassas City MO.
[3]	Bernese (1999) Bernese GPS Software Manual, University of Bern.
[4]	Biberger, R.J., Teuber, A., Pany, T. and Hein, G.W. (2003) Development of an APL Error Model for Precision Approaches and Validation by Flight Experiments. In: ION (Editor), GPS/GNSS, Portland, OR, pp. 2308-2317.
[5]	Bouska, C.T.J. and Raquet, J.F. (2003) Tropospheric Model Error Reduction in Pseudolite Based Positioning Systems. ION GPS/GNSS 2003, Portland OR, USA, pp. 390-298.
[6]	Choi, I.K., Wang, J., Han, S. and Rizos, C. (2000) Pseudolites: a new tool for surveyors? 2nd Trans Tasman Survey Congress, Queenstown, New Zealand, pp. 141-149.
[7]	Coleman, T.F. (2006) Optimization Toolbox. The MathWorks, Natick, MA, USA.
[8]	Cramer, M., (2003) Integrated GPS/inertial and digital aerial triangulation: Recent test results. In: D. Fritsch (Editor), Photogrammetric Week '03, Herbert Wichmann Verlag, Heidelberg, pp. 161?72.
[9]	Dai, L., Wang, J. and Rizos, C. (2001) The role of pseudosatellite signals in precise GPS-based positioning. Journal of Geospatial Engineering, 3(1): 33-44.
[10]	Grejner-Brzezinska, D. (1997) Airborne Integrated Mapping System: Positioning Module. In: ION (Editor), 53rd ION Annual Meeting, Albuquerque, New Mexico, pp. 225-235.
[11]	He, X., Yang, G. and Chen, Y. (2005) Pseudolite-Augmented GPS For Deformation Monitoring: Analysis and Experimental Study. International Symposium on GPS/GNSS. The Hong Kong Polytechnic University, Hong Kong.
[12]	Hofmann-Wellenhof, B., Lichtenegger, H. and Collins, J. (2000) GPS Theory and Practice. Fifth revised edition. Springer- Verlag/Wien, New York, 382 pp.
[13]	Kwon, J.H. and Jekeli, C. (2001) A new approach for airborne vector gravimetry using GPS/INS. Journal of Geodesy, 74: 690-700.
[14]	Lee, H.K., Wang, J., Rizos, C., Barnes, J., Tsujii, T. and Soon, B.K.H. (2002) Analysis of Pseudolite Augmentation for GPS Airborne Applications. 15th Int. Tech. Meeting of the Satellite Division of the U.S. Inst. of Navigation, Portland, Oregan, USA, pp. 2610-2618.
[15]	Lewis A. L. (1996) Airborne Kinematic GPS Position for Photogrammetry: The Determination of the Camera Exposure Station, Digital Photogrammetry: An Addendum to the Manual of Photogrsmmetry.
[16]	RTCA (2000) GNSS Based Precision Approach Local Area Augmentation System (LAAS)-Signal-in-Space Interface Control Document (ICD). RTCA/DO-246A, Radio Technical Commission for Aeronautics.
[17]	Wang, J. (2002) Applications of pseudolites in geodetic positioning: Progress and problems. Journal of Global Positioning Systems, 1(1): 48-56.
[18]	Wang, J.G. (2005) Modelling and geometry design for pseudolite augmented airborne DGPS, 18th Int. Tech. Meeting of the Satellite Division of the U.S. Institute of Navigation,. ION, Long Beach, California, USA.
[19]	Wang, J.G., Wang, J., Lee, H.K., Sinclair, D. and Watts, L. (2004) Tropospheric Delay Estimation for Pseudolite Positioning, The 2004 International Symposium on GNSS/GPS, Sydney, Australia.
[20]	Zhang, Y. and Barton, C.G. (2005) A real-time meteorologicalbased troposphere (RMT) correction with integrity bound for long baseline DGPS, GPS Solutions, 9(4): 255-272.