Abstract: | The largest source of error uncertainty in current Space-based Augmentation Systems, which are single frequency (L1), is the ionospheric delay. In the coming years, the deployment of new signals in L5 will allow civil users to estimate and remove the ionospheric delay in the pseudoranges. This will have a large impact on the planned dual frequency Satellite Based Augmentation Systems (SBAS). Once the ionospheric delay error uncertainty is removed, the Protection Levels will decrease substantially, and other error sources will dominate. The remaining terms in the error bound are much less critical than the ionospheric delay error bound in the current single system, so it is likely that they can still be optimized. This is true in particular for the User Differential Range Error (UDRE) and Message Type 28 (MT28) algorithms which compute the clock and ephemeris error bounds. In [1], we outlined the main elements of a covariance based joint UDRE and MT28, which took into account both biases and receiver faults. Simulations showed that it could reduce VPLs by 20%, potentially enabling more demanding operations like Cat. II approaches. The improvements did not depend on a change in the message standards. In [2], we showed that this algorithm could even bring benefits to the current single frequency Wide Area Augmentation System WAAS, by making coverage less sensitive to the loss of a single satellite, and by strengthening coverage on the coasts of the U.S. In this work, we further develop and evaluate with WAAS prototype data the algorithm that was presented in [1]. In the first section, we will describe the basic elements of the algorithm, in particular how to overcome the fact that the matrix defined in Message Type 28 is only sent every 120 s, (when the time to alarm is 6 s). In the second part, we will set the tunable parameters of the algorithm and the algorithm using WAAS prototype data. This data is taken from a WAAS prototype that matches the current WAAS operational system. We will evaluate the performance of the algorithm using L1 and L2 pseudorange data and compare it to the current UDRE and MT28 algorithm to determine whether its implementation SBAS would be worthwhile. |
Published in: |
Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida |
Pages: | 3270 - 3276 |
Cite this article: | Blanch, Juan, Walter, Todd, Enge, Per, Stern, Abe, Altshuler, Eric, "Evaluation of a Covariance-based Clock and Ephemeris Error Bounding Algorithm for SBAS," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 3270-3276. |
Full Paper: |
ION Members/Non-Members: 1 Download Credit
Sign In |