InSARTrac: a novel approach for remote acquisition of 3D slope displacement vectors

The recent advent of terrestrial interferometric synthetic aperture radar (InSAR) has greatly enhanced the ability of monitoring slope deformation. However, the displacements obtained are one-dimensional, offering little insight into the underlying deformation mechanism. This study summarizes an approach for obtaining three-dimensional slope displacement vectors through the integration of InSAR and two-dimensional image feature tracking (FT) technologies. The method, referred to as InSARTrac, uses a single digital camera oriented in the InSAR line of sight (LOS) generating time-lapse imagery, from which FT extracts (sub-) pixel shifts of pixel clusters. The 1D LOS InSAR measurements are vectorially combined with the 2D normal to the LOS FT measurements to obtain the 3D displacement vector. Bench-scale target displacement tests using a high precision translation for displacement and reference gave a 3D accuracy of 0.05 mm at a distance of 13 m, which corresponds to 1.3 mm at 500 m, assuming linear behaviour. These initial results indicate that InSARTrac can provide a reliable means for obtaining accurate 3D slope displacement vectors remotely and without the use of reflectors. Current studies are focused on implementing InSARTrac in a number of different field environments to investigate outdoor measurement accuracy and the range of potential applications.