## 3 GNSS Data Collection and Processing Methodology  
For data collection, two hours of GPS/Galileo observations with a 30 s interval are collected using the Xiaomi 11T module over a base point located in Aswan, Egypt, on Days of Year (DOY) 70, 71, and 72 (Figure 1). Thereafter, the acquired datasets from the smartphone are converted into RINEX format using the Geo++RINEX mobile (Version 2.1.6) application [29]. The reference point was established using 4.5 h of raw GPS data collected from a geodetic receiver (i.e., Trimble R4S), which was subsequently processed through the CSRS-PPP online service using the final precise products [30]. The characteristics of the smartphone GNSS datasets are outlined in Table 1.  
Figure 1: Xiaomi 11T is mounted on a wooden base, with its center aligning with the reference point. The quantity check is applied to our acquired dataset by computing the percentage of GNSS measurements to the total number of epochs. For this purpose, the open-source RINEX SCAN GNSS (Version 1.0.0) software [31] was utilized, which supports multi-GNSS system data quantity through a user-friendly graphical interface (GUI). Table 2 summarizes the quantity check outputs for GPS/Galileo measurements on DOY 71. Galileo signals experience greater data losses compared to those of GPS, particularly in carrier phase measurements. The datasets are processed using the open-source Net-Diff GNSS (Version 1.14) software, which is capable of processing GNSS data through PPP approaches, as well as data processing and output analysis [32; 33]. Given that just 17 GPS satellites transmit the L\({}_{5}\) signal, it is expected that the total number of processed GPS satellites may not be enough for the PPP solution [34]; therefore, a pre-mission plan was employed using the Trimble GNSS online service [35]. As illustrated in Figure 2, the number of processed satellites for GPS-only (G), Galileo-only (E), and combined GPS/Galileo (GE) varies depending on the type of products used, even for the same PPP solution, which affects the Position Dilution of Precision (PDOP) factor. \begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline
**System** & **Frequency** & \multicolumn{4}{c}{**Code**} & \multicolumn{2}{c}{**Observations**} \\  & & **Code** & **Carrier** & **Doppler** & **Signal Strength** \\ \hline GPS & L\({}_{1}\) & C1C & L1C & D1C & S1C \\  & L\({}_{5}\) & C5Q & L5Q & D5Q & S5Q \\  & E\({}_{1}\) & C1C & L1C & D1C & S1C \\ Galileo & E\({}_{\text{Sa}}\) & C5Q & L5Q & D5Q & S5Q \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The attributes of Xiaomi 11T GPS/Galileo raw data. \begin{table}
\begin{tabular}{l l l l l l l l l l} \hline \hline
**PRN** & **C1C \%** & **L1C \%** & **C5Q \%** & **L5Q \%** & **PRN** & **C1C \%** & **L1C \%** & **C5Q \%** & **L5Q \%** \\ \hline G32 & 100 & 98.6 & 100 & 100 & E34 & 100 & 99.9 & 100 & 18.7 \\ G27 & 100 & 100 & 100 & 100 & E30 & 100 & 99.6 & 100 & 99.4 \\ G26 & 100 & 100 & 100 & 100 & E27 & 100 & 100 & 100 & 100 \\ G23 & 100 & 100 & 100 & 100 & E26 & 100 & 98.9 & 100 & 95.5 \\ G18 & 100 & 100 & 100 & 100 & E21 & 100 & 100 & 100 & 100 \\ G10 & 100 & 100 & 100 & 100 & E15 & 100 & 100 & 100 & 100 \\ G08 & 100 & 99.6 & 100 & 97.3 & E13 & 100 & 100 & 100 & 100 \\ E03 & 100 & 99.7 & 100 & 99.9 & E08 & 100 & 99.9 & 100 & 99.9 \\ E01 & 100 & 71.8 & 100 & 87.5 & E07 & 100 & 100 & 100 & 99.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: GPS and Galileo measurements availability on DOY 71. Figure 2: _Cont._  
To assess the quality of the collected raw GNSS data, the average C/N0 was calculated for both GPS and Galileo satellites (Figure 3). It can be seen that the average C/N0 values of the GPS L\({}_{1}\) and Galileo E\({}_{1}\) are superior to that of the GPS L\({}_{5}\) and Galileo E\({}_{5a}\) with the exception for satellites E19 on DOY 70 as well as satellite E05 on DOY 72, also it is obvious that the average C/N0 values for all GPS satellites are superior to those of Galileo satellites.