# Designation of the Quality of EGNOS+SDCM Satellite Positioning in the Approach to Landing Procedure
###### Abstract
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* There is no common solution for EGNOS and SDCM positioning in the context of aviation;
* In numerical terms, no algorithms exist that would integrate the single EGNOS and SDCM solutions for the purposes of determination of the resultant position of the aerial vehicle;
* In terms of aviation, there are also no available mathematical formulas that would enable the determination of the accuracy, continuity, availability, and integrity from a combined navigation solution of EGNOS and SDCM;
* In aviation, more research is required to determine the SBAS positioning quality for specific phases of flight, e.g., landing approach;
* Another missing element in the aviation context is the increased number of trainings of flight crews in Multi-SBAS positioning for aviation purposes. The conducted analysis of the state of knowledge together with preliminary conclusions and identification of the missing elements in the research on the subject matter of this article revealed that it is necessary to develop and implement a new SBAS navigation solution in aviation based on the integration of data from EGNOS and SDCM. Due to that, this article presents a modified plan of an SBAS navigation solution based on the Multi-SBAS positioning concept. Namely, first of all, the Multi-SBAS concept enables to determine the resultant coordinates of an aerial vehicle, and secondly, it allows for the integration of single SBAS solutions. Based on this assumption, single SBAS navigation solutions are combined through the appropriate model of the resultant position of the aerial vehicle. Subject literature demonstrates [61] that the optimum model for the determination of the resultant position of an aerial vehicle is the weighted mean model. It should be noted that this approach will also require the modification of the scheme of determining the quality parameters of SBAS positioning. Moreover, it may be assumed that the accuracy, continuity, availability, and integrity parameters of SBAS positioning will also have the nature of resultants if this approach is used. Here it should be explained why this calculation strategy is so beneficial. This is due to the fact that the determined resultant accuracy, continuity, availability, and integrity parameters of SBAS positioning will be defined with at least one degree of freedom [61]. This means that, in statistical terms, the presented solution, has one redundant measurement and it involves calculation control, which will enable, at least, to reduce gross errors in a single SBAS solution, if such errors occur. It is still necessary to pay attention to the very scheme of connecting individual SBAS solutions in the data integration model. Namely, the weighted mean model used to integrate individual SBAS solutions depends on the weights assigned to measurements. In the presented study, weighting was applied as a function of the inverse number of tracked GPS satellites for which corrections were developed from EGNOS and SDCM geostationary satellites. This weighing scheme is important due to several reasons: firstly, it is easy to implement in calculations and does not require the user to possess specialist statistical knowledge; secondly, most GNSS receivers in the process of processing GNSS observations provides the users with access to information about the current number of tracked GPS satellites; and thirdly, the measurement weight model will also depend on the geometric coefficient PDOP (Position DOP). The modified Multi-SBAS positioning model presented here may be used to improve the quality of SBAS positioning in aviation. Apart from that,the proposed Multi-SBAS solution may also be used in the certification process of SBAS supporting systems in aerial navigation.