# Designation of the Quality of EGNOS+SDCM Satellite Positioning in the Approach to Landing Procedure
## 3 Research Experiment
In order to perform the pre-processing of the analysed material, GPS satellite data were saved on portable data carriers and then uploaded to the computer. After that, the data were converted from the binary format to the RINEX format. As a result, two RINEX files in the GPS system were obtained: observation RINEX and navigation RINEX. At this  
Figure 4: The PDOP value from single SBAS solution. Figure 3: The number of GPS satellites with SDCM and EGNOS corrections. stage, the corrections from the EGNOS satellite number S123 were also applied as well as SDCM corrections from satellite number S125. The corrections are published on the server [[ftp://serenade-public.cnes.fr/SERENAAD0](ftp://serenade-public.cnes.fr/SERENAAD0)]([ftp://serenade-public.cnes.fr/SERENAAD0](ftp://serenade-public.cnes.fr/SERENAAD0)) (accessed on 30 November 2021) [72]. The format of the EGNOS and SDCM corrections was saved in files with the \"EMS\" extension. The prepared GPS navigation and observation data in the RINEX format and the SBAS corrections in the EMS format were then used in the third phase of research. At this stage, calculations were performed with use of the RTKLIB software v.2.4.3 [73] and the programming language Scilab v. 6.0.0 [74]. Calculations began in the RTKLIB navigation application. Here, the RTKPOST library was used to determine the position of the aerial vehicle from a single SBAS solution (EGNOS and SDCM). The SBAS positioning algorithm in the RTKPOST software is based on the SPP code method with the implementation of SBAS corrections [62]. For a single SBAS solution, two calculation reports were generated: one from a single GPS solution with EGNOS corrections and the other from a single GPS solution with SDCM corrections. Due to the fact that the determination of the parameters of the positioning of aerial vehicle requires us to determine the reference trajectory of the flight, the reference position of the Diamond DA 20-C aircraft was determined from the RTK-OTF solution in the RTKLIB software. The RTK-OTF solution adopted in the RTKLIB application is the \"MOVING BASE\" computational module [75]. The RTK-OTF solution uses the RINEX observation data from the on-board receiver and the reference station and the GPS navigation message. As for the reference station, RINEX observation data from the OPNT base station [76] located in Olsztyn were used. The generated reports from a single SBAS solution and the RTK-OTF differential technique were then used to conduct further numerical calculations, i.e., to determine the resultant position of the aerial vehicle and the resultant quality parameters of MultiSBAS positioning in the landing approach procedure. Calculations were performed in the Scilab programming language. Calculations performed in the Scilab software started with importing the reports generated in the RTKPOST application. Then, the necessary determined navigation parameters in the period from 11:38:31 h (41,911 s) to 11:55:59 h (42,959 s) according to system time GPST were selected. The next stage consisted in the development and application of the weighted mean model in compliance with the adopted research methodology. This stage involved the determination of: the resultant coordinates of the aerial vehicle, the standard deviations for these resultant coordinates, and the resultant quality parameters of positioning from the multi-system SBAS solution. The calculations took into account the mathematical algorithms for Equations (1)-(9). The results of the calculations performed in Scilab software are presented in form of numerical data, tables and graphics in Section 4. It is worth mentioning, that some additional numerical calculations were also conducted in the Scilab software to confirm the correctness of the proposed research method. They are discussed in Section 5.