# Evaluation of Low-Cost GNSS Receiver under Demanding Conditions in RTK Network Mode
## 3 Results
### Urban Canyon Conditions  
The last station was located in difficult measuring conditions for GNSS technology (Figure 12). On the west side the horizon was directly limited by a building, while on the east side by a line of tall trees--the tripod was set up along an alley running between a park and a large football stadium. Figure 11: Cumulated diagrams with results of measurements at the Pt 6 station (obscuring the horizon from many directions; differences in relation to the reference points with standard deviations [m]). Figure 10: Cumulated diagrams with results of measurements at the Pt 5 station (obscured horizon from the west and the top; differences in relation to the reference points with standard deviations [m]). It is worth mentioning the problems that were encountered during the measurements. As many as eight series of measurements were performed on this station. The Leica GS18T receiver had a fixed solution only in half of the series. The ZED-F9P receiver with the Leica AS10 antenna had even fewer fixed solutions--only three. The same receiver, but with the ANN-MB-00 antenna, had fixed solutions in four series. Unfortunately, the result of one of them differed considerably from the reference coordinates--by as much as 13 m on the vertical coordinate. This measurement was removed from further considerations, nevertheless the result is still not satisfactory. The measurement results (values only from measurements with a fixed solution) are presented below (Table 8). The cumulative graphs representing the measurement results at the Pt 7 station are presented below (Figure 13). It is worth noting that the scale of the vertical axis has been changed from the previous graphs due to the large values of coordinate differences and standard deviations when measuring with the ANN-MB-00 antenna. Figure 12: Field conditions at the Pt 7 station. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Receiver** & & **Coordinate** & **Ref. Difference** & **St. Deviation** \\ \hline \multirow{3}{*}{GS18T} & X [m] & 5,548,075.284 & \(-\)0.004 & 0.029 \\  & Y [m] & 7,422,190.919 & 0.001 & 0.047 \\  & H [m] & 205.945 & \(-\)0.032 & 0.057 \\ \hline \multirow{3}{*}{ZED-F9P + AS10} & X [m] & 5,548,075.344 & \(-\)0.064 & 0.075 \\  & Y [m] & 7,422,190.954 & \(-\)0.033 & 0.106 \\  & H [m] & 205.875 & 0.038 & 0.015 \\ \hline \multirow{3}{*}{ZED-F9P + ANN-MB-00} & X [m] & 5,548,075.259 & 0.021 & 0.110 \\  & Y [m] & 7,422,190.852 & 0.069 & 0.147 \\ \cline{1-1}  & H [m] & 205.676 & 0.237 & 0.392 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Measurement results on Pt 7. The best result was finally achieved by the Leica GS18T. As it is a professional geodetic receiver, its advantage over the low-cost u-blox ZED-F9P was expected. Nevertheless, it had not been apparent until the measurement on this station. Previously, the Leica GS18T has achieved even slightly worse results than the u-blox ZED-F9P configuration with the Leica AS10 antenna. However, in the last station the measurement was not problem-free--the receiver had 4 fixed position solutions for 8 measurements done. On the other hand, when the measurement was already taken with such a solution, then the appropriate accuracy was kept (in contrast to one measurement by ZED-F9P with ANN-MB-00 antenna) and the differences were on a similar level to the stations presented before. The conditions influenced noticeably also the standard deviations. The configuration of the u-blox ZED-F9P + Leica AS10 antenna coped reasonably well. The problems that the receiver had in these conditions can be seen both in the type of the solution and the differences in relation to the reference coordinates, as well as in the values of the standard deviations. The ANN-MB-00 antenna definitely did not cope with the signals reflected from the surrounding building and trees, which turned into a significant loss of accuracy, especially in the vertical plane. An additional disappointment was the solution marked as the fixed one while the difference between the reference coordinates exceeded 13 m.