## 3 Results  
### Quality Check of GNSS Observations  
The results of the quality check of the stations considering four parameters (INT, MP, CSR, SNR) are presented in Table 5; however, for the single frequency receivers, it was not possible to analyze the quality of the observations because at least two frequencies are required. The linear combination between carrier phase and pseudo-range observations in L1 and L2 is necessary for the estimation of the root mean square (RMS) [54]. The percentage of the integrity of the stations varied between 78% and 100%, the obtained results could be related to the locations (urban areas). CULC presented the highest quality values, due to being a reference station with open sky. The minimum recommended value for the integrity is 95%, where only CULC1, CULC2 and, CULC3 stations with 97%, 100% and 100%, respectively, exceeded this value. The stations named \"CULC1-3\" are the same, the assigned number is for proper identification for the static relative process. EST5 and CULC4 stations are within the limit as shown in Figure 5 (where the horizontal red line represents the recommended value). The rest of the stations do not show a good integrity performance, which is related to the surrounding environment. The LCDF station has the lowest integrity with 78%. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Parameters for PPP Method**} \\ \hline
**Software** & **CSRS-PPP [46]** \\ \hline Observable & Code \& Phase \\ \hline Elevation cut off angle (deg) & 7.5 \\ \hline Satellite orbits & Precise (IGS) \\ \hline Satellite products input & CLK-RINEX \\ \hline Sampling rate (s) & 1, 2, 15 \\ \hline Troposphere model & Saastamoinen [47] \\ \hline Relativistic effects & Corrected [48] \\ \hline Receiver antenna phase center correction & IGS antex \\ \hline Ambiguity resolution & PPP-AR [49] with the new actualization [50] \\ \hline Phase wind-up-effect & Applied [51] \\ \hline Solid Earth Tides correction & Applied [52] \\ \hline Reference Frame & ITRF \\ \hline \multicolumn{2}{c}{Parameters for static relative positioning} \\ \hline Software & Topcon Tools [53] \\ \hline Observable & L1 \& L2; L1 \\ \hline Elevation cut off angle & 15\({}^{\circ}\) \\ \hline Receiver antenna phase center correction & IGS antex \\ \hline Method & Static relative \\ \hline Sampling rate (s) & 1, 2, 15 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of parameters used in the PPP and static relative positioning methods. LCDF shows the highest degree of multipath effect in both bands and may be related to the observation time and the percentage of integrity. However, CULC1, 2, 3, and 4, despite showing a good percentage of integrity and a longer observation time, also exceed the value recommended by the IGS of 0.30 m for the multipath effect as shown in Figure 6, where the stations with the least affectation are EST3 and EST6. With the signal-to-noise ratio and the multipath effect, a weak SNR would be expected in most stations, since both variables have an inversely proportional behavior [55], however, this only occurs in the stations EST1, EST3, and EST6. The other stations show a directly proportional relationship, where EST1 shows a strong signal in L\({}_{1}\) and a weak signal in L\({}_{2}\). Furthermore, other dual-frequency receivers show strong signals on both bands, as well as the single-frequency receivers shown in Figure 7, where the red line shows the limit between strong signals \(\geq\) 36 dBHz and weak signals \(<\) 36 dBHz, being a quality check parameter that reflects the signal tracking and capturing performance.