Tropospheric Delay Estimation for Pseudolite Positioning

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ABSTRACT

Pseudolites, ground-based GPS signal transmitters, can significantly enhance the GPS satellite geometry or can even be an independent positioning system. However, as pseudolites are very close to the receivers, error effects are different from the traditional GPS and should be considered and modeled in a different way. Tropospheric delay is one of the largest error sources in pseudolite positioning, as pseudolite signalpropagates through the lower troposphere which is very difficult to be modeled due to spatial variations in atmosphere. The objective of this research is to analysepseudolite tropospheric delay modelling methods and to select the optimal tropospheric delay models for differentapplications. Several methods to estimate the tropospheric delay for pseudolite positioning are introduced and compared. One approach is to utilize single-differenced GPS tropospheric models. Another one is to compute the tropospheric delay as a function of the local refractivity along the pseudolite signal path. The ratio method used for Electronic Distance Measurement (EDM) can also be applied to estimate tropospheric delay. Experiments with simulation and real flight test data are conducted in this study to investigate the proposedmethods. The advantages and limitations of each method are analysed. The mode defined by RTCA and its modification are suitable for a low elevation and short range application, such as LAAS and local ground based applications. Models derived from single-differenced NMF and Saastamoinen models perform well in long range and high elevation but have a big bias in low elevation. And the model derived from the Hopfield model performs relatively well in all the range andelevation.

Cite this paper

J. Wang, J. Wang, D. Sinclair and H. Lee, "Tropospheric Delay Estimation for Pseudolite Positioning," Positioning, Vol. 1 No. 9, 2005, pp. -.

Conflicts of Interest

The authors declare no conflicts of interest.

References

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