Facing Strong Ionosphere in SBAS Systems: Comparison of Different Techniques for Ionosphere Estimation

J. Arenas, B. Ochoa, M.E. Ramírez, A. Sainz, and E. Sardón

Abstract:	The Satellite Based Augmentation System (SBAS) constitutes an augmentation of the Global Navigation Satellite Systems (GNSS), such as GPS or GLONASS, which provides safe and reliable use of satellite signals for certain safety critical uses such as civil aviation. For single-frequency users, the largest source of positioning errors comes from ionospheric activity, irregular, too local, and in several cases difficult to predict. In this paper it is presented the comparison between some methods that are currently used in operational SBAS systems to estimate the vertical ionospheric delay at each ionospheric grid point. The first one is based on the combination of a Kalman Filter with a triangular mesh interpolation (Solar-TRIN). From the slant Total Electron Content (TEC) values measured in the ionospheric pierce points, it is computed the TEC values on a spherical grid of points, fixed with respect the Sun, and whose electron content is assumed to be constant. The second methodology is based on Kriging interpolation, a well-known method applied in several geostatistics fields. This interpolation method uses known sample values and an assumed covariance function (variogram) to determine unknown values at different locations and times, taking benefit of the spatial correlation of TEC in the ionosphere. In addition, it also provides a measurement of the estimation uncertainty, which is got in a natural manner when computing the estimates. Finally, a third method is considered, combining the advantages from the two first techniques, in particular using Kalman filtering and considering spatial correlation by means of a variogram, like in Kriging interpolation. Some experimental examples are also included, showing the comparison of the results obtained with those methods against known reference values of ionospheric delay, as well as the accuracy levels achieved when applying one or another methodology.
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:	1153 - 1162
Cite this article:	Arenas, J., Ochoa, B., Ramírez, M.E., Sainz, A., Sardón, E., "Facing Strong Ionosphere in SBAS Systems: Comparison of Different Techniques for Ionosphere Estimation," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 1153-1162.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In