摘要
The ionospheric disturbances affect Global Positioning System (GPS) performance in terms of accuracy and integrity, especially over the equatorial region.During disturbances, GPS receivers suffer from high noise levels, and the distribution of the noise has non-Gaussian tails.Effects of ionospheric disturbances are not taken into account by the current stochastic model.This paper develops a statistical solution that can mitigate effects of ionospheric disturbances on GPS accuracy and integrity using a commercial dual frequency receiver.Rate of TEC Change Index (ROTI), a parameter derived from the dual frequency receiver, is used to group the levels of ionospheric disturbances.The standard deviations of the pseudorange noise under different groups are evaluated.Incorporating both ROTI and the satellite elevation, we present a modified stochastic model from many years GPS data for weighing GPS measurements to reduce the effects of the disturbed observation on the positioning accuracy.The performance of the model is confirmed by an experiment.On other hand, an inflated sigma for each group is recommended for overbounding anomalies of observations to protect the user against threats of ionospheric disturbances.The technique together with results in this paper can be used to mitigate the effects of ionospheric disturbances on GPS in future.
