Availability prediction method for EGNOS

Following the recent development of wide-area differential technology, satellite-based augmentation systems (SBASs) have been applied in many fields. However, the capability of monitoring stations used for generating error correction might degenerate with the aging of ground equipment over time, and the poor geometry between ranging and integrity monitoring stations (RIMS) and satellites could affect the reliability of navigation systems in supplying safety of life service. Therefore, it is necessary to predict SBAS availability so that users can choose a safe and efficient navigation system. Predictions of user difference range error indicator (UDREI) and grid ionospheric vertical error indicator (GIVEI) are the two difficulties in predicting SBAS availability. Considering the effect of geometry on UDREI, satellite geometric dilution of precision is defined to distinguish different geometries such that the relationship between the number of visible RIMS and UDREI in different geometries can be obtained. With regard to the effect of geometry on GIVEI, a weighted number of visible ionospheric pierce points (IPPs) is defined to describe the geometric IPP distribution such that the relationship between the number of visible IPPs and GIVEI in different geometries can be achieved. Finally, experiments are performed to evaluate the effectiveness of our proposed method. With the prediction algorithm, the prediction is consistent with actual performance over 75.17% of the entire European region. In particular, when focusing on central Europe, where the distribution of RIMS is uniform, the level of consistency can reach 95–100%. It can be concluded that the prediction performance of the algorithm is encouraging and that this model may be considered a good contender for predicting SBAS availability.