# Accuracy of Code GNSS Receivers under Various Conditions
## 5 Conclusions  
The present engineering work was aimed at investigating the accuracy of GNSS code receivers under limited visibility conditions. The obtained measurement data from the survey instruments were compared with the measurement results of a Javad Triumph-1 surveying instrument operating in RTK mode. Due to the limited visibility of the celestial sphere (presence of tall trees and close proximity of high buildings), the number of precision solutions was very low. As a result of the analysis of the measurement results of the three studied objects, the best accuracies were noticed for the static point measurement. Additionally, in this study, a better reliability of the results obtained from cell phones was noticed than with the Garmin receiver using GPS. The deviation values of the NE components for the smartphone X_1 were predominantly in the range up to 3 m, but compared to the other phones, the measurement was less stable due to the larger errors present (\(\pm\)15 m). Horizontal coordinate errors ranged from 1.2 to 2.8 m, while the standard deviation ranged from 2.4 to 2.5 m. For phone X_2, the NE deviations were within 1 m in the first half of the measurement and within 3 m in the second half. Horizontal coordinate errors ranged from 0.6 to 1.1 m, while the standard deviation ranged from 0.3 to 1.2 m. The X_3 smartphone provided the most stable measurements, maintaining values within 2 m for both horizontal coordinate components throughout the measurement. All phones were running the same software and mode and, apart from a few outlier observations at the beginning of the measurement with the X_1 receiver, they showed a high consistency and potency. They used only the GPS system. The results of measurements with these receivers were similar and the values of deviations in NE components did not exceed 3 m for all tested smartphones. While testing the measurement accuracy with receiver G_1 for NE components, it was noticed that the deviations did not exceed the value of 13 m, while for G_2, the limit was 3 m. The application installed on the smartphones did not record altitude, so only the Garmin receivers were subjected to the U component deviation test. The G_2 receiver obtained 3 times smaller mean horizontal coordinate errors and twice smaller NE standard deviations compared to the G_1 receiver. During the point measurement, the deviations in the elevation component (U) for G_1 ranged from 7 to 11 m, while for G_2, it was from 7 to 10 m. Both receivers recorded a constant error, and its value did not exceed 11 m. For all three NEU components, the G_1 receiver, which operated in GPS mode, received worse accuracies than the G_2 receiver using GPS+GLONASS mode. When measuring the point with the phones, better accuracies were noted for the handheld receivers by up to 10 m.  
The worst accuracies were observed during the linear measurement in motion. As a result of the analysis of the results, a drop in the receiving signal was noticed for all tested receivers (at 12:22:32), which affected the accuracy of both the horizontal coordinates and the altitude coordinate. During the measurement, a loss of the measurement signal of receiver X_1 was noticed, which was characterized by the registration of the last recorded point until the end of the measurement. The phone did not stop recording data, probably due to the app being programmed to do so. The other two smartphones (X_2, X_3) produced similar point plots. The deviations in the N component did not exceed 19 m, while for the E component, it was 7 m. The position determination error with the cell phone was 8 to 11 m for the N component and up to 2 m for the E component. Smartphone receivers showed high consistency and repeatability of measurements. The largest errors were in the north-south direction, according to the direction of measured line. During the analysis of the accuracy of the handheld receivers, it was observed that the graphs of the horizontal coordinate components were similar to each other.