# Designation of the Quality of EGNOS+SDCM Satellite Positioning in the Approach to Landing Procedure
###### Abstract
Here, it is worth mentioning publication [5], which presented a combined EGNOS+SDCM positioning solution as part of the positioning of UAV (Unmanned Aerial Vehicles). Moreover, publications [47; 48; 49; 50] describe the characteristics of the SDCM system in terms of its application as a system to support the SBAS in air navigation. On the other hand, publication [51] presented the influence of the SDCM system of the availability parameter of SBAS positioning for the entire globe, while publication [52] discussed the influence of the SDCM system on the determination of the accuracy, availability, and integrity of GNSS positioning for the territory of South Korea. Publications [53; 54; 55; 56] presented the influence of the SDCM system on the accuracy parameter of GPS positioning and of positioning with the GPS/GLONASS (Globalnaya Nawigacionnaja Sputnikovaya Sistema) systems. Yet another study [57] analysed the possibilities to use the SDCM supporting system in aerial operations in the territory of Romania in reference to the EGNOS and GAGAN (GPS Aided Geo Augmented Navigation) systems. A very interesting numerical solution was presented in publication [58]. Namely, it presented selected models of SBAS corrections for the supporting systems: SDCM, EGNOS, WAAS (Wide Area Augmentation System), MSAS (Multi-functional Satellite Augmentation System) and GAGAN, followed by their comparison. Article [59] discussed a new algorithm to modify the SDCM corrections for the purposes of their application to improve GLONASS positioning, whereas study [60] presented the influence of the SDCM solution on the determination of the equipment delay for the receiver between GPS/GLONASS systems. The presented knowledge status analysis [1; 2; 3; 4; 5; 60; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31] allows us to draw the following conclusions:  
* The quality parameters of SBAS positioning are very important in terms of the application of SBAS systems in aviation;
* The studies of quality parameters of SBAS positioning were usually based on a single SBAS navigation solution;
* In Poland, the EGNOS supporting system was generally used in practically all the referenced research projects [3; 4; 5; 60; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31];
* In research projects conducted in Europe and Africa [32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46], the EGNOS system was also used as a system to support the SBAS;Subject literature [47; 48; 49; 50] shows that the SDCM system was less widely applied in practice in aviation than the EGNOS system;
* However, it also demonstrates [47; 48; 49; 50] that the SDCM system may provide an alternative for the EGNOS system in GNSS satellite positioning;
* The area of the territory of Poland is covered by the common range of corrections of EGNOS and SDCM, so that both SBAS supporting systems are used in GNSS satellite positioning. Additionally, the presented analysis of the state of knowledge [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60] also allows us to define the missing elements that constitute current research problems for the proposed topic of the article, i.e.