# Designation of the Quality of EGNOS+SDCM Satellite Positioning in the Approach to Landing Procedure
###### Abstract  
The main aim of this paper is to present the results of research on the application of a modified mathematical model to determine the quality parameters of SBAS (Satellite Based Augmentation System) satellite positioning in aviation. The authors developed a new calculation strategy to determine the resultant values of the parameters of accuracy, continuity, availability and integrity of SBAS positioning. To achieve it, a weighted mean model was used for the purposes of developing a mathematical algorithm to determine the resultant values of SBAS positioning. The created algorithm was implemented for two SBAS supporting systems, i.e., ECNOS (European Geostationary Navigation Overlay Service) and SDCM (System of Differential Correction and Monitoring). The algorithm was tested in a flight test conducted with a Diamond DA 20-C airplane in north-eastern Poland in 2020. The conducted research revealed that the resultant error of the position in 3D space determined with use of the proposed weighted mean model improved by, respectively, 1-7% in comparison to the standard arithmetic mean model and by 1-37% in comparison to a single SBAS/EGNOS solution. Moreover, the application of the Multi-SBAS positioning algorithm results in an increase in the nominal results of continuity and availability by 50% in comparison to the arithmetic mean model. Apart from that, the values of the integrity parameters determined with use of the proposed weighted mean model improved by 62-63% in comparison to the standard arithmetic mean model. accuracy; integrity; availability; continuity; E  
The SBAS system should be compatible with a specific GNSS system, e.g., with the GPS (Global Positioning System);  
The SBAS system should provide an additional code phase navigation signal at the carrier frequency L1 of 1575.42 MHz;  
The SBAS system should monitor the current status of the constellation of the given GNSS system with which it is compatible and interoperable;  
The SBAS system should transmit two main differential corrections, i.e., the correction of ephemeris data and GNSS satellite clock correction;  
Finally, apart from that, it is required that every SBAS system should determine the ionospheric correction precisely and calculate the tropospheric correction in compliance with the RTCA-MOPS (Radio Technical Commission for Aeronautics--Minimum Operational Performance Standards) model. Due to that, the following technical parameters were adopted in Annex 10 for the SBAS navigation solution [2]:  
The pseudo-range error from SBAS satellite cannot exceed 25 m;  
The probability that the range error exceeds 150 m in any hour shall not exceed \(10^{-5}\);  
The probability of unscheduled outages of the ranging function from an SBAS satellite in any hour shall not exceed \(10^{-3}\);  
The SBAS service area shall be a defined area within an SBAS coverage area where SBAS meets the relevant requirements;  
The carrier frequency is 1575.42 MHz within a \(\pm\)12 MHz band;  
The signal of SBAS satellites should be within the range of -161 dBW to -153 dBW;  
The difference between SNT (SBAS Network Time) and GPST (GPS time) shall not exceed 50 nanoseconds. On the other hand, the use of SBAS support in the context of aviation applications refers mainly to selected landing approach procedures of aerial vehicles and to the related determination of the quality parameters of SBAS positioning. This applies first of all to the SBAS APV-I (Approach with Vertical Guidance-I) procedure and the SBAS APV-II (Approach with Vertical Guidance-II) procedure [3].