Deformation monitoring using GNSS-R technology

Abstract

The use of Global Navigation Satellite System Reflectometry (GNSS-R) as an opportunity for remote sensing applications has drawn increasing attention in recent years. A variety of applications have been developed and can be generally characterized into two groups: the non-geometrical applications such as sea state monitoring and biomass monitoring, which are usually focusing on the amplitude or the power of the reflected signals; the geometrical applications such as sea level monitoring and snow depth monitoring, which are focusing on the range difference between the direct and reflected signals, and centimeter level accuracy has been achieved through these applications. The idea of using GNSS-R for deformation monitoring is inspired by the remarkable achievement of the GNSS-R geometrical applications. Diversified equipment and technologies are available nowadays to fulfill the deformation monitoring tasks, such as onsite monitoring (i.e., GNSS, leveling, and tilt sensor) and offsite monitoring (i.e., photogrammetry, Interferometric Synthetic Aperture Radar (InSAR), microwave radar and Light Detection and Ranging (LiDAR)). To realize the application of deformation monitoring using GNSS-R technology, the measurement of sub-centimeter accuracy is desired. Moreover, various deformation situations, such as kinematic and quasi-static deformation, require differently to the monitoring methods. Towards this goal, the ranging accuracy of GNSS-R needs to be improved, and different monitoring approaches need to be developed for various deformation cases. If done, this new application possesses the advantages of low labor-consuming and low time-consuming considering the remote working mode. In view of the other methods like photogrammetry, InSAR, or LiDAR, the benefits of applying the GNSS-R approach rest in lower expense, easy implementation and higher update rate. Aiming at this purpose, this thesis devotes to present the investigation on the feasibility of using GNSS-R for deformation monitoring. Three different kinds of algorithms, which suit continuous, discontinuous and relative deformation monitoring cases, have been proposed in this thesis. Sub-centimeter level accuracy has been achieved through various experiments. To maximize the availability of implementing this application, the proposed approaches can be adopted to both software-defined radio (SDR) receiver and commercial GNSS receiver, which will lower the barrier of using GNSS-R technology. In addition, the suitability has been analyzed to evaluate the practicability of the proposed methods in terms of different types of reflecting surfaces, monitoring distances and the deformation period. Furthermore, the benefits and limitations of all proposed methods are also discussed.