# GNSS Multipath Detection Using Continuous Time-Series C/N0
## 4 Testing and Results
### Test Results in the First Location  
The experiment was performed in a dense urban environment near Tokyo station in Tokyo, Japan, on May 27, 2020. The configuration of the receiver and antenna used in all three tests is presented in Table 3. The car was parked at the edge of the road and a standard patch antenna was attached to the car rooftop. The sampling rate of the measurement data was 1 Hz. The satellite systems and frequencies used in this test were GPS/QZSS L1C/A and L2C, Galileo E1 and E5B, GLONASS G1 and G2, and BDS B1 and B2. The L2P signals of the GPS and GEO satellites of BDS were not used because they were not available in this GNSS receiver. The total data recording period was 1800 s. Postprocessed RTK positioning was used to estimate the precise reference position. As mentioned in Section 3, the positioning software used in this study was developed in our laboratory. The same positioning software was used for all three tests. The common settings without our proposed method for the satellite selection are listed again in Table 4. The residuals in the least-squares method were checked repeatedly provided that the absolute residual was over 10 m. The test location was very close to the case of Section 2.1 illustrated in Figure 2. Moreover, five images around the car are presented in Figure 13 to provide a better understanding of the situation around the antenna. There were approximately three to four lanes on each side of the road and several high-rise buildings with different heights on both sides. Several trees and a large iron signboard over the car were also present. \begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Parameter** \\ \hline Mask angle & 15 degrees \\ Maximum HDOP & 10.0 \\ Minimum C/N\({}_{0}\) for L1 band & 32 dB-Hz \\ Minimum C/N\({}_{0}\) for L2 band & 32 dB-Hz \\ Pseudo-range measurements & Tracked \\ Carrier phase measurements & Tracked \\ Carrier phase measurements (only RTK-GNSS) & Tracked and half-cycle resolved \\ Threshold for residual (least-squares method) & 10.0 m \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Common parameters for satellite selection. \begin{table}
\begin{tabular}{c c} \hline \hline
**Sensor** & **Model Name** \\ \hline GNSS receiver & u-blox F9P (base/rover) \\ GNSS antenna (rover) & Standard patch antenna (ANN-MB-00-00) \\ GNSS antenna (base) & Trimble Zephyr 2 Geodetic \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Configurations of sensors used in the test. The horizontal errors of the DGNSS are depicted in Figure 14. The horizontal errors of the DGNSS were occasionally reduced by the residual checks; however, very large errors remained. The maximum absolute horizontal error in the DGNSS was 91.13 m, and the 90 th percentile value was obtained as 37.80 m. The standard deviations in the horizontal direction for E and N were 16.75 and 6.13 m, respectively. The average errors in the horizontal direction for E and N were \(-\)8.49 and \(-\)2.11 m, respectively. The accuracy was not improved in the case in which different minimum C/N\({}_{0}\) values were set, namely 35 and 40 dB-Hz. In reality, no correct fixes of the RTK-GNSS occurred, although the fix rate was 12.4%. The fix rate was calculated by dividing the total epochs by the number of fixed solutions. If the absolute horizontal error was less than 10 cm and the absolute height error was less than 20 cm from the true position, the solution was regarded as the correct fix. It was difficult for the RTK-GNSS to resolve correct ambiguities because the absolute position deduced from the pseudo-range based on the DGNSS was mostly deviated and unstable. Figure 14: DGNSS horizontal errors. Figure 13: Detailed images around the antenna.