## 4 Discussions
The results from Table 10 for 2D displacements also highlight the superior performance of the Survey Calibrated antenna, as its MAE is 0.2 mm, while the MAE values are 0.9 mm and 1.0 mm for the Survey and Tallysman antennas, respectively. For 3D displacements, the MAE values of Survey and Tallysman are 1.0 mm and 1.1 mm, while for Survey Calibrated, the value is smaller (0.3 mm). It can beemphasized here that the MAE of 2D displacements is smaller than that of 3D in all cases, while for 1D, the value of MAE is greater since the number of imposed movements (sample size) differed between the two tests. The Survey Calibrated antenna has known calibration parameters even though it is a low-cost antenna. Based on the results presented in Table 10, Survey Calibrated had higher displacement accuracy in all cases, and its performance was better than the two uncalibrated antennas: The displacement accuracy was almost the same between them but lower than that of Survey Calibrated. Differences between true and estimated 1D, 2D, and 3D movements are shown graphically in Figure 5. The variations are again in favor of Survey Calibrated for 1D, 2D, and 3D displacements. Variations are larger for 1D differences, while the 2D and 3D differences have almost the same variations. The differences from the true values of displacements obtained with geodetic network adjustment (Figure 6) are smaller compared with those estimated from baseline vectors only (Figure 5). In the static test (PPP), low-cost devices showed satisfactory performance. The RMSE for horizontal components is at the sub-centimeter-level for east (6.1 mm) and north (3.1 mm) components for the Survey Calibrated antenna. The ellipsoid height estimated with GNSS observations has lower precision compared with the horizontal components, and the uncertainty of the ellipsoid height for Survey Calibrated is 10.8 mm (Table 11). For the Tallysman antenna, the values of RMSE are 6.3 mm, 5.1 mm, and 11.7 mm for the east, north, and ellipsoid height, respectively (Table 11). Spatial displacements of 20 mm were detected by both antennas: The Tallysman antenna detected 88.9% of imposed movements, while Survey Calibrated detected 91.7% (Table 12). Displacements greater than 20 mm were detected by both antennas in all cases. The MAE is 5.4 mm for Survey Calibrated and is greater (7.4 mm) for Tallysman (Table 13). The comparison of low-cost and geodetic instruments showed better performance for the latter. In all cases (all satellites from all systems), the number of cycle slips is higher for the low-cost instruments compared with the geodetic ones, but the increase is not significant (Figure 9). After all, there are still enough continuous GNSS data for each ambiguity to be estimated with sufficient quality. The represented RMS values in the graphs in Figure 10 show slightly higher values of phase noise for low-cost GNSS instruments (red bars) compared with the noise of phase observations obtained with geodetic GNSS instruments (blue bars). However, the noise level of low-cost GNSS instruments is still at the millimeter level, which assures a millimeter level of derived results, i.e., adjusted coordinates or baseline components.