## 1 Introduction  
The main purpose of SBASs (Satellite-Based Augmentation Systems) is to support civil aviation tasks. However, due to their ability to improve the quality parameters of GNSS positioning, they can also have other applications [1; 2; 3; 4]. The operation of SBAS systems relies on the use of geostationary satellites to transmit correction data and other information that can improve GNSS positioning. EGNOS is a European system based on the transmission of data using three geostationary satellites. In addition to EGNOS, the main SBAS group includes the US WAAS (Wide Area Augmentation System), Russia's SDCM (System of Differential Correction and Monitoring), Japan's MSAS (Multi-functional Satellite Augmentation System), India's GAGAN (GPS-Aided Geosynchronous Augmented Navigation System), China's Beidou SBAS BDSBAS, and Australia's SouthPAN (Southern Positioning Augmentation Network) [5]. With real-time transmitted data, EGNOS can significantly improve the accuracy of autonomous positioning using code-based observations [6; 7; 8]. Depending on the observation conditions and measurement equipment, real-time accuracy of several tens of centimetres can be achieved. In [9], EGNOS was used to integrate a measurement system with INS (Inertial Navigation System) for autonomous ships in Inland Waterways. In turn, Ref. [10] investigated the impact of using EGNOS for Remotely Piloted Aircraft System (RPAS) positioning. In 2016, a smartphone with the ability to record raw GNSS data using the Android Nougat operating system was made available for the first time [11; 12]. Over time, the capabilities were increased in terms of the types of observations that could be recorded, starting with GPS data at L1 frequency. In 2018, a Xiaomi Mi8 smartphone running on the Broadcom BCM47755 GNSS chipset was made available to users, characterised by the ability to record full GNSS observations including L5 GPS, QZSS frequencies, and E5a Galileo [13; 14]. Today, many mobile devices offer similar capabilities. A significant problem with recording raw GNSS data with smartphones is duty cycling, which is a process during which the smartphone's chipset runs in discontinuous mode. This results in a saving in battery consumption, but at the same time activates cycle slips during positioning. In paper [15], the results of the effect of duty cycling on GNSS code and phase observations were presented. Currently offered Android-based mobile devices are very often not using duty cycling, as is the case for the Xiaomi Mi8. The ability of smartphones to record raw GNSS data has led to a great number of application uses. The paper [16] presents the use of raw GNSS data acquired with a smartphone for geophysical applications. The paper [17] presents the possibilities of using raw GNSS data in SPP (single-point positioning) and PPP (precise point positioning) using a smartphone. Raw satellite observations acquired with a smartphone are also being investigated for new concepts in RTK (real-time kinematic) positioning technology [18], as well as anti-spoofing and anti-jamming solutions [19]. The paper [20] presents the results of horizontal single-point positioning for smartphone measurements based on raw GNSS data and frequency E5. The root mean square error of these measurements was at the level of 4.57 m. The paper [21] presents the results of a multi-GNSS single-frequency (L1/E1/B1/G1) positioning solution obtained by Huawei P30 with a horizontal RMS of 3.24 m. On the other hand, the use of raw GNSS data on smartphones for DGNSS positioning can yield accuracy results of 1.5 m [22]. According to [23], by augmenting smartphone positioning with EGNOS and DGNSS corrections, it is possible to obtain a horizontal accuracy of better than 1 m with 95% availability.