An overview to remotely sensed displacement measurements fusion: Current status and challenges

At the end of the 20th century, the development of spatial geodetic techniques (optical & SAR imagery, GPS) has allowed for drastic improvement of the spatial coverage and the resolution of the displacement measurements. The arrival of these techniques has caused an effective revolution by significantly improving our ability to measure the ground movement, as well as their temporal evolutions with great precision over large areas. Spectacular results have been obtained in numerous applications with displacement of various characteristics (in terms of magnitude, duration, spatial distribution): the study of subsidence in urban areas, of the co-seismic, inter-seismic and post-seismic motions, of glacier flows, of volcanic deformation, etc. Nowadays, the displacement maps obtained by remote sensing techniques cover almost the whole world, with a precision within millimetres per year. Therefore, they are considered as the predominant sources for studies of the terrestrial deformation, from which geophysical models of the deformation have been retrieved to further understand the deformation source in depth. To this end, good knowledge of the reliability of the remote sensing data, as well as of the physical models accordingly obtained is crucial for all the researches and applications that use these sources of information. A perspective of significant improvement in the accuracy of the displacement measurement appears with the growing availability of remote sensing data. Methodological development in fusion of displacement measurements and of the integration of a physical model based on the supercomputer facilities seems necessary to reduce the uncertainty and to improve the accuracy of the displacement measurement. In this context, this paper addresses the current status, challenges and perspectives of the remotely sensed displacement measurement fusion.