Rock salt has remarkable mechanical properties and high economic importance; however, the strength of salt compared to other rocks makes it a rather vulnerable material. Human activities could lead to acceleration of the dissolution of soluble rock salt and collapse of subsurface caverns. Although sinkhole development can be considered a local geological disaster regarding the characteristic size of surface depressions, the deformations can result in catastrophic events. In this study we report the spatiotemporal evolution of surface deformation in the Solotvyno salt mine area in Ukraine based on Sentinel-1 interferometric synthetic aperture radar measurements. Although the mining operations were finished in 2010, several sinkholes have been opened up since then. Our results show that despite the enormous risk management efforts, the sinkholes continue to expand with a maximum line-of-sight deformation rate of 5 cm/yr. The deformation time series show a rather linear feature, and unfortunately no slowdown of the processes can be recognized based on the investigated 4.5-year-long data set. We utilized both ascending and descending satellite passes to discriminate the horizontal and vertical deformations, and our results revealed that vertical deformation is much more pronounced in the area. Analytical source modeling confirmed that the complex deformation pattern observed by Sentinel-1 radar interferometry has a direct connection to the former mining activity and is confined to the mining territory. With the 6 d repetition time of Sentinel-1 observations, the evolution of surface changes can be detected in quasi real time, which can facilitate disaster response and recovery.

Ground and infrastructure stability are important for our technologically based civilization. Infrastructure projects take into consideration the risk posed by ground displacement (e.g., seismicity, geological conditions and geomorphology). To address this risk, earth scientists and civil engineers employ a range of measurement technologies, such as optical/laser leveling, GNSS and, lately, SAR interferometry. Currently there is a rich source of measurement information provided in various formats that covers most of the industrialized world. Integration of this information becomes an issue that will only increase in importance in the future. This work describes a practical approach to address and validate integrated stability measurements through the development of a platform that could be easily used by a variety of groups, from geoscientists to civil engineers and also private citizens with no training in this field. The platform enables quick cross-validation between different data sources, easy detection of critical areas at all scales (from large-scale individual buildings to small-scale tectonics) and can be linked to end-users from various monitoring fields and countries for automated notifications. This work is closing the gap between the specialized monitoring work and the general public, delivering the full value of technology for societal benefits in a free and open manner. The platform is calibrated and validated by an application of SAR interferometry data to specific situations in the general area of the Romanian Carpathians and their foreland. The results demonstrate an interplay between anthropogenically induced changes and high-amplitude active tectono–sedimentary processes creating rapid regional and local topographic variations.

There are potentially dangerous areas where InSAR technology cannot be applied routinely in the absence of proper persistent or distributed scatterers. Here, we planned and investigated the use of truncated trihedral triangle corner reflectors (CRs) oriented to ascending and descending directions for Sentinel-1 orbit, which were mounted on the optimal concrete basement including an additional global navigation satellite system (GNSS) adapter. These integrated benchmarks were designed to produce a signal-to-clutter ratio of about 100 (i.e., 20 dB). The mechanical design allows optimal orientation of the reflectors and resistance against dynamic effects. We investigated 1:5 models of the CRs and integrated benchmarks in an anechoic chamber to estimate the effects of truncation and the interference of the twin reflectors. The main effect of the interference is the asymmetric monostatic radar cross section, which can be neglected. The integrated benchmarks were also investigated in two recent landslide areas in Hungary using Sentinel-1 single look complex (SLC) scenes, which confirmed that the preliminary requirements can be met.

We present a new procedure and program system to integrate Sentinel-1 synthetic aperture radar (SAR) interferometry and Global Navigation Satellite System (GNSS) network observations to estimate 3-D surface changes caused by environmental processes. The procedure is based on the integrated geodetic/geodynamic benchmarks, which are equipped with both ascending (ASC) and descending (DSC) corner reflectors. The results of sparse GNSS observations are interpolated using the ASC and DSC line-of-sight changes provided by the Sentinel-1 mission every six days. The data integration is carried out using a Kalman filter where north, east, and up (vertical) coordinates and their instantaneous velocities are estimated and updated by the GNSS-derived data. The north components are essentially provided by the GNSS observations alone. The procedure was developed and successfully tested on landslide areas in Hungary.

Geodetic/geodynamic benchmarks, equipped with both ascending and descending radar corner reflectors, and a method for integrated InSAR and GNSS/GPS network observation were developed and applied as the continuation of the former geodetic monitoring at the Dunaszekcső landslide, Hungary. The attempts to apply InSAR technologies using archive and Sentinel-1 data practically failed on the most intensive landside areas (“Vár” and “Szent János” hills), where proper persistent or distributed scatterers were not found. Our concept solved this problem, where the Simple Look Complex (SLC) images are used to interpolate the movements between two GNSS network observations using the integrated benchmarks and the method of Kalman-filtering. Since the InSAR line-of-sight (LOS) changes are barely sensitive to the north movements, this information is essentially provided by GNSS measurement alone, moreover, the GNSS measurements are used to: a) identify the benchmarks, b) detect the unwrapping errors and missing cycles and c) provide the boundary values of Kalman-filtering.After the installation of benchmarks three GPS observations were carried out and 69 ascending and 61 descending Sentinel-1 A and B images were processed. The data processing properly indicated the general movement history, which fit the curves of former geodetic observations, as well. The dense data points of the East and Up (vertical) components made possible more detailed geomorphologic interpretations of the ongoing process between two GPS observations. During the investigated periods the deceleration of movements was experienced, however, the deceleration of the dormant state needs the continuation of the monitoring.