# Low-Cost Dual-Frequency GNSS Receivers and Antennas for Surveying in Urban Areas
###### Abstract  
Low-cost dual-frequency global navigation satellite system (GNSS) receivers have recently been tested in various positioning applications. Considering that these sensors can now provide high positioning accuracy at a lower cost, they can be considered an alternative to high-quality geodetic GNSS devices. The main objectives of this work were to analyze the differences between geodetic and low-cost calibrated antennas on the quality of observations from low-cost GNSS receivers and to evaluate the performance of low-cost GNSS devices in urban areas. In this study, a simple RTK2B V1 board u-blox ZED-P9P (Thalwil, Switzerland) was tested in combination with a low-cost calibrated and geodetic antenna in open-sky and adverse conditions in urban areas, while a high-quality geodetic GNSS device was used as a reference for comparison. The results of the observation quality check show that low-cost GNSS instruments have a lower carrier-to-noise ratio (C/N\({}_{0}\)) than geodetic instruments, especially in the urban areas where the difference is larger and in favor of the geodetic GNSS instruments. The root-mean-square error (RMSE) of the multipath error in the open sky is twice as high for low-cost as for geodetic instruments, while this difference is up to four times greater in urban areas. The use of a geodetic GNSS antenna does not show a significant improvement in the C/N\({}_{0}\) and multipath of low-cost GNSS receivers. However, the ambiguity fix ratio is larger when geodetic antennas are used, with a difference of 1.5% and 18.4% for the open-sky and urban conditions, respectively. It should be noted that float solutions may become more evident when low-cost equipment is used, especially for short sessions and in urban areas with more multipath. In relative positioning mode, low-cost GNSS devices were able to provide horizontal accuracy lower than 10 mm in urban areas in 85% of sessions, while the vertical and spatial accuracy was lower than 15 mm in 82.5% and 77.5% of the sessions, respectively. In the open sky, low-cost GNSS receivers achieve a horizontal, vertical, and spatial accuracy of 5 mm for all sessions considered. In RTK mode, positioning accuracy varies between 10-30 mm in the open-sky and urban areas, while better performance is demonstrated for the former. GNSS; surveying; low-cost receivers; low-cost antennas 20232328612339052861233905286123390528  
nas makes those GNSS devices more competitive with geodetic ones that are much more expensive [9]. Low-cost dual-frequency GNSS receivers were tested by researchers in relative, absolute, and real-time kinematic (RTK) positioning modes in both static and kinematic tests, and satisfactory positioning performance was obtained [10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24]. The performance of these devices in combination with patch antennas was evaluated in urban areas, considering RTK [19], static, relative, and absolute positioning modes [25; 26]. [PERSON] et al. [11] used low-cost GNSS receivers and different geodetic and low-cost antennas to estimate the zenith tropospheric delay (ZTD). The authors concluded that ZTD from low-cost GNSS devices is comparable to ZTD determined on a basis of high-ended geodetic devices. In the case of [15], the zero baseline and short baseline tests were performed to evaluate the quality of the u-blox receiver and the calibrated and uncalibrated low-cost antennas. The zero baseline test shows that ZED-F9P has low noise, in the millimeter range, while the results from the short baseline test prove that the calibrated antennas have better performance in comparison to the low-cost uncalibrated antennas used. In the study in [14], low-cost GNSS receivers were tested for geodetic monitoring purposes at short baselines, while low-cost and geodetic GNSS receivers were used as reference stations. Results indicate that 10 mm spatial displacements can be detected in half-hour sessions, even when only low-cost GNSS devices are used.