## 2 Related Papers  
The problem of determining an aircraft's actual position using the PPP method has been presented and described in many research papers worldwide. Most research papers on PPP positioning in air navigation had described and presented position solutions using GPS (Global Positioning System) or GLONASS (Globalnaja Nawigacionnaja Sputnikovaya Sistema) navigation systems. That is, of course, related to the fact that only GPS and GLONASS systems are certified by ICAO for GNSS satellite navigation in aviation [1]. It can be concluded that GPS and GLONASS, as global GNSS navigation systems, provide continuous satellite positioning in aviation. The literature review provides a multi-faceted approach to the application of the PPP measurement technique in air navigation. Reference [6] propose using a PPP solution to determine the position of an aircraft with respect to the differential solution from the AUS-POS program. The aircraft's position was determined in the CSRS-PPP (Canadian Spatial Reference System-Precise Point Positioning) program using the least-squares method for GPS observations. The maximum coordinate difference between the GAPS (GPS Analysis and Positioning Software) and AUSPOS (online GPS processing service) solution was up to \(\pm\)0.5 m for the horizontal coordinates and \(\pm\)1 m for the vertical coordinate. In turn, the paper [7] proposed the use of a PPP solution to determine the position of a helicopter with respect to a DD (Double Difference) differential solution in postprocessing. The helicopter position was determined in the P3 (software developed by the University of Calgary) software package using Kalman filtering for GPS observations. The maximum coordinate difference between the PPP solution and the differential DD solution reached \(\pm\)0.5 m for all ENU (East-North-Up) components. A similar solution was proposed in work [8], in which helicopter positioning accuracy was determined using the P3 (software developed by the University of Calgary) software package with the PPP method. The initial positioning accuracy of the helicopter was about 2.7 m, while, in the final phase of the flight, it was higher than 0.1 m for BLh (B: Latitude, L: Longitude and h: ellipsoidal height) coordinates. In paper [9], P3 software was used to determine the positioning accuracy of an aircraft flying at high speed. The values of positioning errors of the aircraft between the PPP solution and the differential DD solution were up to \(\pm\)0.2 m for the horizontal coordinatesand \(\pm\)1.1 m for the vertical coordinate. However, paper [10] used the PPP method to determine a helicopter's position with respect to the KGPS (Kinematic GPS) solution in the PNAV program. The helicopter position was determined using Kalman filtering for GPS observations. The maximum coordinate difference between the PPP solution and the KGPS PNAV solution was up to \(\pm\)1 m for all ENU components. Furthermore, in work [11], the PPP method was used to determine the UAV (Unmanned Aerial Vehicle) position in GIPSY and RTKLIB software. The UAV reference position was determined using the DGPS (Differential GPS) technique for GPS phase observations. The paper presents different scenarios for UAV position determination for the PPP method: iterative method, filtering of GPS observations and the smoothing of code observations by GPS phase observations. The maximum coordinate difference between the PPP and DGPS solutions reached \(\pm\)1 m for all ENU components. In paper [12], the PPP method's accuracy in PP-RTX software was investigated in more than 100 flight tests. The PP-RTX solution's typical accuracy with respect to the ASB (Applanix Smartbase) differential solution was up to \(\pm\)0.2 m for all ENU components. In turn, the paper [13] proposed to test the PPP method in TriP, IT and GraftNav software in a flight experiment. This paper presented the results of the comparison of the aircraft coordinate determination between the TriP, IT, GraftNav software and the GPSSurvey baseline solution.