Estimate the Ionospheric vertical delay in augumentation data of SBAS

Abstract

In order to use GPS for civil air navigation, augmentation for GPS is needed. In the ICAO (International Civil Aviation Organization), SARPs (Standards And Recommended Practices) for GNSS including SBAS (Satellite Based Augumentation System) is under development.

The ionospheric delay is the main error source of GPS ranging, except SA (Selective Availability). In general, the ionospheric delay can be corrected by using eight parameters in the message that is transmitted by GPS satellite. However, only 50% of the delay error can be corrected by those parameters. In the SBAS, single frequency (L1) receivers are employed. The ionospheric vertical delay correction parameters at ionospheric grid points are transmitted from geo-stationary satellite for correction of ionospheric error.

This paper describes how to estimate the ionospheric delay by some methods and comparison of estimation accuracy for some methods. By using the distance-Klobucher method, we can create the ionospheric delay map. The map shows that the distance-Klobuchar method can improve accuracy of delay estimation near pierce points.

From these results, it is confirmed that the distance-Klobuchar method is useful for the ionospheric delay estimation of the SBAS.