Augmented positioning with CORSs network services using GNSS mass-market receivers

Abstract

Over the last twenty years, positioning with low cost GNSS sensors has become widespread worldwide at both commercial and academic level. The Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the precision achievable when using mass-market GNSS receivers with a network of permanent GNSS station (also called CORSs network - Continuous Operating Reference Stations) for various purposes. The aim of this study is to investigate real effect and the role of the CORSs Network for this type of receivers, and especially how the products generated by the CORSs network can be used to improve the level of accuracy and precision if mass-market receivers are considered. The rapid development and diffusion of the GNSS network which provides a positioning service has enabled us to use single frequency receivers both in post-processing and real time approach by means of virtual RINEX and differential corrections. In the first approach, in order to determine the possible level of accuracy and precision obtainable with this sensor, a special test field was carried out which enabled us to study the variation of position with millimetrical accuracy. Tests were carried out considering various types of receivers (geodetic and mass market) and antennas (patch and geodetic) in static mode. The static test was carried out by acquiring raw data for 24 hours and dividing them into small parts (5, 10 or 15 minutes each), in order to consider the effect of the acquisition time on the final results and also consider the complete constellation. The postprocessing was performed with a commercial software. An interesting advantage is the possibility of generating a VR close to the rover position especially when mass market sensors are used, with the aim of creating a short (few meters) baseline, or in extreme cases it is possible to realize a null baseline thus eliminating the bias with the double differences in a relative positioning. By using a VR we obtain an independent solution in respect to the master-rover distance in attempt of fixing the ambiguity phase. The real-time experience was carried out with mass-market receivers for NRTK (Network Real Time Kinematic) positioning within the Regione Piemonte CORSs network. Two network products were used (VRS® and nearest correction): RTKLIB software was used in order to apply these corrections to the raw data of the mass market receivers. Some very good results were obtained which are reported in this paper.