Effective Monitoring of Ground Instability with SFMC GNSS Network

NSL's “STICK” is a SFMC IMU-integrated GNSS device developed for the precise monitoring of movement and deformation, either sudden or gradual. The single frequency chipset uses the GPS, GLONASS and Galileo constellations. After getting promising results from experimental results (i.e. precise and accurate detection of movement from cm to mm level), in 2017 and 2018 NSL have deployed several networks of STICK units throughout the United Kingdom. A particularly interesting case study started in October 2017 with a GNSS network monitoring of 15 STICK devices being deployed in an area surrounding a section of rail track on the West Highland Line in Scotland. Current positions are 1-2cm accurate and automatically obtained server-side following the Real Time Kinematic technique. However, the actual displacement is usually smaller than or comparable to the precision of the measurements. Hence, statistical strategies, including bootstrapping, are adopted to analyze the GNSS processing results for the evaluation of the presence of movement with a certain level confidence. For the case study discussed here, the analysis of the stochastic processes produces trend lines representing movement at the 1mm level. In this paper, we present and discuss the technical challenges and the results NSL is achieving from live case study of continual monitoring of ground instability affecting transport infrastructures.