Special issue: terrestrial remote sensing for areal deformation monitoring

Abstract

The development of new instruments, sensing techniques, and algorithms has opened a new era in the field of terrestrial deformation monitoring and related applications. Robotic total stations with reflector-less range measurement and increasingly also image assistance (Scherer and Lerma 2009), terrestrial laser scanners (Vosselman and Maas 2010), and digital photogrammetry (Barazzetti et al. 2010) allow the acquisition of dense point clouds within a short time, thus yielding detailed snapshot representations of surfaces and a basis for measuring deformations over wide areas. In addition, ground-based interferometric radar (Monserrat et al. 2014) can be used to derive differential deformation with very high resolution, in particular with respect to persistent scatterers as discussed already by Ferretti et al. (2001). The amount of data provided by these systems is typically much larger than with traditional geodetic techniques, and they potentially represent areal deformations without a need for generalization from displacements of a few carefully selected control points. However, there is no direct point-topoint correspondence between the point clouds obtained at different epochs and thus entirely new algorithms are required in order to analyze deformations (see Dermanis (2011) and Fuentes Santibanez (2012)). New concepts for areal deformation monitoring (ADM) are being developed and investigated including instrumental advances, sensor and process models, and data processing techniques. All of these require thorough validation and assessment before they can be safely applied in critical monitoring applications. This special issue features six selected contributions originally presented at the 2nd Joint International Symposium on Deformation Monitoring (JISDM) held in Nottingham on September 2013 and subsequently further elaborated for peer review and publication. They introduce new instrumental developments, compare technologies and review the state-ofthe-art with respect to their impact on areal deformation measurements, and propose new methods for deformation analysis. The affiliations of the authors of these papers are located in different countries across the globe (Germany, Greece, Italy, the Netherlands, People’s Republic of China, Switzerland, the UK), highlighting internationally recognized relevance of research into areal deformation monitoring. The first article in the special issue (Papastamos et al. 2015) describes the application of total stations for the measurement of control point 3-D displacements with nearly millimeter accuracy. During a project for the excavation of the Athens underground metro railway, this technique was exploited to assess tilting of some chimneys resulting from ground deformation due to tunneling. While such deformations are usually assumed as a 2-D effect, here the theodolite measurements pointed out the evidence of clear 3-D rigid movements of the chimneys in different directions. This outcome was in full agreement with the new theoretical models of ground deformations in the investigated area. * Alessandro Capra capra.alessandro@unimore.it