## 2 Materials and Methods
### GNSS Data Processing and Analysis  
To assess the performance of the PPP method as well as its achieved precision, results were compared with the static relative method considering two cases such that in case 1, low-cost and geodetic receivers with dual and single frequency are utilized. In case 2, data was processed in the static relative method considering the CULC reference station of the National Institute of Statistics and Geography, which is located at approximately 20 km, using low-cost and geodetic receivers with dual and single frequencies. Once the coordinates were obtained, the solutions from the dual-frequency geodetic receiver were taken as the reference for the comparison study, using the official reference frame in Mexico (ITRF08 at epoch 2010.0) [15; 43]. In order to evaluate the results obtained by the PPP method, standard deviation was evaluated according to the \"Circle of Probable Error\" (CEP) and \"Vertical Positioning Accuracy\" (EPV) [43]. Mexican gravimetric geoid version 2010 (GGM10) was also used for evaluation with a resolution of 2.5 min of arc, approximately 4.5 km, and a standard deviation of 20 cm, which represent the geoid height as measured in vertical direction [44]. The observation time was set following that presented by [26] based on the PPP method, taking into account that to obtain a horizontal precision of 2 cm, a convergence time of 60 min is necessary. ISL2 station does not meet this  
\begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Receiver** & **Name** & **Sample** & **Elevation** & **Constitution** & **Observation** & **Date of** \\  & & **Rate (s)** & **Mask (\({}^{\circ}\))** & **Constitution** & **Time (h)** & **Observation** \\ \hline \multirow{8}{*}{Geodetic} & Est1 & 15 & 15 & GPS (L1, L2, L2C) + GLONASS & 1.967 & 20 September 2020 \\  & Est2 & 15 & 15 & GPS (L1, L2, L2C) + GLONASS & 1.025 & 20 September 2020 \\  & Est3 & 15 & 15 & GPS (L1, L2, L2C) + GLONASS & 1.025 & 20 September 2020 \\  & Est4 & 15 & 15 & GPS (L1, L2, L2C) + GLONASS & 1.342 & 20 September 2020 \\  & Est5 & 15 & 15 & GPS (L1, L2, L2C) + GLONASS & 2.292 & 20 September 2020 \\  & Est6 & 15 & 15 & GPS (L1, L2, L2C) + GLONASS & 1.525 & 20 September 2020 \\  & ISL1 & 15 & 15 & GPS (L1) & 3.717 & \\  & ISL2 & 1 & 15 & GPS (L1) & 0.8617 & 23 September 2020 \\  & ISL3 & 1 & 15 & GPS (L1) & 1.171 & \\ \hline \multirow{4}{*}{Low-cost} & LCSF & 1 & 15 & GPS (L1) & 2.06 & 23 September 2020 \\  & LCDF & 2 & 15 & (L1, L2) + GALILEO (E1, E5b) & 2 & 23 September 2020 \\  & & & & + BEIDOU (B1) & & \\ \hline References & \multirow{2}{*}{CULC} & \multirow{2}{*}{15} & \multirow{2}{*}{15} & GPS (L1, L2, L2C) + GLONASS & 24 & According to \\  & Station & & & & & & observations \\ \hline \hline \end{tabular}
\end{table}
Table 3: Characteristics of the GNSS observations.  
criteria, however, it can be considered to evaluate the same convergence time through a single-frequency receiver [45] in an urban area. The static relative method was conditionate to the Mexican CORS at 15 s, in the case of the PPP method, the observation was decimate to 30 s [46] according to the new actualization for the CSRS-PPP software. The summary of the parameters used for processing the observations using the PPP and the static relative method are presented in Table 4.