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Over the past two decades, low-cost single-frequency Global Navigation Satellite System (GNSS) receivers have been used in numerous engineering fields and applications due to their affordability and practicality. However, their main drawback has been the inability to track satellite signals in multiple frequencies, limiting their usage to short baselines only. In recent years, low-cost dual-frequency GNSS receivers equipped with Real-Time-Kinematic (RTK) engines entered the mass market, addressing many of the limitations of single-frequency GNSS receivers. This review article aimed to analyze the observations and positioning quality of low-cost GNSS receivers in different positioning methods. To provide answers to defined research questions, relevant studies on the topic were selected and investigated. From the analyzed studies, it was found that GNSS observations obtained from low-cost GNSS receivers have lower quality compared to geodetic counterparts, however, they can still provide positioning solutions with comparable accuracy in static and kinematic positioning modes, particularly for short baselines. Challenges persist in achieving high positioning accuracy over longer baselines and in adverse conditions, even with dual-frequency GNSS receivers. In the upcoming years, low-cost GNSS technology is expected to become increasingly accessible and widely utilized, effectively meeting the growing demand for positioning and navigation. [ABSTRACT FROM AUTHOR]

Dense Global Navigation Satellite System (GNSS) observations are beneficial for monitoring the small-scale troposphere turbulence in both spatiotemporal domains. Densification of current geodetic GNSS networks can be achieved by incorporating low-cost GNSS receivers and antennas, benefitting weather monitoring. This study aims to focus on real-time tropospheric delay estimation using real-time GNSS data streams collected by low-cost GNSS receivers and antennas. The results indicate that: (1) Low-cost GNSS devices can offer accuracies of 7.5 mm in winter and 10.8 mm in summer for real-time zenith tropospheric delay (ZTD) estimations; (2) By applying the phase center variation corrections for low-cost GNSS antennas, which are often ignored in previous studies on low-cost GNSS applications, can produce more reliable real-time ZTD estimations; (3) Low-cost GNSS devices can capture the ZTD fluctuations under heavy precipitation events in a real-time mode, showing a great potential as sensors to monitoring severe weather. These results underscore the viability of low-cost GNSS devices as cost-effective sensors that complement geodetic GNSS equipment in real-time troposphere monitoring and forecasting, especially at small scales. Their integration aids in the densification of existing monitoring networks, thereby bolstering GNSS meteorology applications. [ABSTRACT FROM AUTHOR]