Long-term Monitoring of Displacements by Digital Image Analysis

It is often very difficult to perform a long-term monitoring programme to measure displacements of structures in remote areas like high rock buttes in alpine regions, where the direct installation of measurement devices and a constant reading is, due to low accessibility, not possible or too expensive. In most cases, tape extensometers or distance measurement instruments have to be installed directly on the moving rock part and a continuous reading is necessary, unless an electronic device records the measurements. The analysis of digital images to calculate the relative position of reference targets, as a form of remote sensing, seems to be an adequate alternative.
This paper investigates the applicability of digital image analysis to perform long-term monitoring programmes with digital cameras. Therefore, the movement of a mobile reference target in relation to a stationary target will be detected on scaled digital images and back-calculated with MATLAB. The thesis shall be tested in field work previously with simplified conditions to detect the limitations of and requirements on the system as well as the accuracy and the influencing factors, like the atmosphere or a dynamic camera position. Afterwards, the method shall be applied on an actual example of a potentially instable rock tower close to Nötsch (Carinthia) to detect displacements along the shear bands and the total movement of the whole rock tower. Advantage of this technique would be the one-time installation of the reference targets in accessible areas and the constant reading of the displacements by remote sensing.