## 1 Introduction
In the dynamic scenario, the horizontal accuracy was not greater than 20 mm, and lower accuracy was obtained for ellipsoid height. In the case of [24], the dual-frequency u-blox receiver (ZED-F9P) was evaluated in Precise Point Positioning (PPP) Zenith Tropospheric Delay (ZTD) with different types of geodetic and low-cost antennas. The obtained results indicate that low-cost receivers can provide quality results of ZTD. The relative calibration of the u-blox antenna was shown to improve the performance of the GNSS device and provide results comparable to the high-end geodetic antennas used in the case study. The study in [15] tested the same GNSS devices in different experiments, in which the relative and absolute positioning modes were evaluated. The ambiguity fixed rate was around 80% and no more than 60% over baselines of 26 km, and more than 50 km,respectively. In PPP, an accuracy of a few centimeters was achieved in short sessions, and in RTK mode, the precision was lower than that provided by the manufacturer, but the use of a geodetic GNSS instrument was shown to improve the performance. Single-frequency C94-M8P receivers with Trimble Bullet 360\({}^{\circ}\) antennas were used to monitor the Mota di Cavezzo bridge in Modena, Italy. Data were acquired at 1 Hz for a month in static and RTK modes. The daily coordinates obtained in static mode had an uncertainty of 1-1.5 mm for the vertical component and less than 1 mm for the horizontal component. The RTK mode provided lower-quality results, which were in the order of 4 mm and 8 mm for the horizontal, and vertical components, respectively [13]. In the study in [18], the u-blox EVK-5T receiver was tested with the external Garmin GA29F antenna, and the Italian CORS was used to provide RTK corrections. Displacements of 10 mm were manually imposed in horizontal and vertical directions. The results were satisfactory, as the percentage of detected movements was higher than 90%. [PERSON] et al. [8] evaluated the EVK-6T u-blox receiver with the ANN-MS antenna, where the test was designed in such a way that baselines of different lengths were observed, and a few permanent stations were used as reference stations. The results indicated that sub-centimeter displacements over short baselines could be detected when long observations were considered. The single-frequency low-cost receiver NEO-7P was tested in conditions similar to real geodetic monitoring, and movements of 25 mm and 35 mm were detected in 2D and 3D, respectively, in short sessions [7]. The u-blox LEA-6T GNSS receiver in combination with Tallysman TW3742 and Tallysman TW3740 was used to monitor San Gaudenzio's Cupola in the city of Novara, located in the northwestern part of Italy. Monitoring was carried out for one year, and the results showed that the old structure moved 20 mm in the vertical direction due to temperature changes, while the horizontal movements were smaller, in the range of a few millimeters [14]. The study in [25] used u-blox EVK8T GNSS receivers and a Garmin antenna for continuous monitoring of a slope with a few millimeters of movement per year. The findings show that these devices can be suitable sensors for applications in risky areas and can be regarded as an alternative to periodic observations that are commonly used for geodetic monitoring. In the case of [26], a low-cost monitoring system in combination with other classical geodetic instruments was used to monitor a landslide in northwest Slovenia. The landslide was monitored for a few months, and displacements were analyzed at nearby points by both devices used. The results suggest that these GNSS devices are suitable for setting up an early-warning system and have satisfactory performance considering their costs. In this work, the low-cost ZED-F9P receiver in combination with three types of low-cost antennas, namely, Survey, Survey Calibrated, and Tallysman TW3882 antennas, was tested in an open-sky environment for displacement detection.