# Low-Cost Dual-Frequency GNSS Receivers and Antennas for Surveying in Urban Areas
###### Abstract
In precise point positioning (PPP) mode, the dual-frequency GNSS receivers were able to detect movements in the magnitude of 20 mm [12]. Those devices were also used for monitoring engineering buildings over short baselines in RTK and static relative mode, and excellent positioning performance was achieved [27]. In the case of [28], such cost-effective equipment was capable of monitoring slow deformations of natural objects with high accuracy. Other researchers found that low-cost GNSS devices are able to provide high position accuracy in static PPP mode when the sampling rate is 1s or less. Accuracy was compromised when using data recorded at 5, 15, and 30 s [13]. The u-blox dual-frequency GNSS chip ZED-F9P and the ANN-MB-00 patch antenna have been tested in open-sky and urban conditions for surveying purposes. In open-sky conditions and for short baselines, accuracy in the centimeter range was achieved in relative positioning mode. However, in the case of urban areas, accuracy was 20 and 15 mm for the horizontal and vertical components, respectively. In RTK mode, the accuracy specified by the manufacturer was not achieved. Uncertainties were larger for both components due to phase center offset (PCO) and phase center variations (PCV) in the patch antennas used [25]. [PERSON] [26] used the same equipment for surveying in urban areas in relative and absolute positioning modes. The results show that both methods can be used for surveying in urban areas in case of optimal surveying conditions. The static relative method had higher accuracy and was suitable for surveying where the accuracy requirements are in the centimeter range. The PPP method was recommended only in the case where the open sky is guaranteed with fewer obstacles for satellite signals. In the study [19], the RTK engine of the u-blox C099-F9P (Thalwil, Switzerland)application board was tested in the open sky, the near-open-sky, in forests, and in urban conditions. The authors conclude that the low-cost receiver works well in the open sky, while the use of a geodetic antenna can significantly improve its positioning performance. The number of scientific articles dealing with the evaluation of low-cost dual-frequency GNSS receivers for surveying purposes in urban areas is very limited. In most cases, open-sky conditions and patch antennas have been used whose PCO/PCV are unknown and are reported to mostly impact height components [14; 25]. The main objectives of this work are two-fold. The first is to analyze the differences between geodetic and low-cost calibrated antennas on the quality of observations from low-cost GNSS receivers and the second is to evaluate the performance of low-cost GNSS devices in urban areas. The structure of the paper has been designed as follows: an overview of various tests of low-cost GNSS equipment is presented, with a particular focus on examining the performance of this equipment in urban areas (Section 1). The study area, equipment used, and methods are shown in Section 2. Then, the results are presented and discussed (Section 3). Finally, the conclusions from the study are listed (Section 4).