Single-Frequency Receivers as Permanent Stations in GNSS Networks: Precision and Accuracy of Positioning in Mixed Networks

Continuous Operating Reference Stations (CORSs) are widely used for many purposes including precise positioning, mapping and monitoring. These architectures are composed of a control centre and a number of permanent stations consisting of geodetic antennas and dual frequency receivers. This infrastructure is costly due to the instruments used and has the additional disadvantage in that inter-station distances between CORSs, that are often too high if a single-frequency receiver acts as a rover. This study focuses on the usefulness of permanent single-frequency stations in order to increase density of existing CORSs for monitoring purposes. In this connection, some innovative GNSS networks composed of geodetic and mass-market L1 receivers have been developed and tested, analyzing the performance of rover positioning in terms of quality, accuracy and reliability in real time. Some tests have been carried out considering different types of receivers (geodetic and mass market) and antennas (patch and geodetic), in real-time mode. The results obtained show that with a “classical” network (where the mean inter-station distances between CORSs are about 40 km) an accuracy of about 5 cm can be achieved after fixing the phase ambiguity with a mass-market L1 receiver acting as rover. In addition, the Time-To-Fix period is very short, being less than 2 min. Despite the obvious fact that increased inter-station distance leads to reduced accuracy, the degree of precision obtainable remains useful for many applications, such as mobile mapping and traffic control. In short, the experiments under examination performed with low-cost GNSS receivers will be useful for many types of applications (landslide monitoring, traffic control), especially where the inter-station distances of permanent GNSS stations are around 40 km.