The monitoring of dams is essential to ensure their safe operation for the production of renewable energy. Common tools to monitor dams are permanently installed plumblines and surveying by means of total station and leveling within a geodetic network. The main drawback of these methods is their limited spatial and temporal resolution. Recent studies have shown promising results using Ground-Based InSAR for geodetic dam monitoring. The fast acquisition speed combined with the surface monitoring capabilities enable to monitor several hundreds to thousands of points on the dam every day or several times a day. However, GB-SAR is a relative phase-measurement technique, and any interruption in the data acquisition leads to difficulties to unwrap differential phase observations and join the disjunct time series. The combination with other absolute measurement tools is promising to create an absolute deformation map of the dam. GNSS is a very efficient and reliable method providing point-wise absolute displacement time series and mm-accuracy. This paper proposes a combination of GNSS and GB-SAR observations to enhance the consistency of the surface-based dam displacement maps obtained by solely GB-SAR measurements. A method to detect unwrapping errors over long time series is proposed. The corrected GB-SAR time displacement maps are compared to a numerical model and confirm the correctness of the applied corrections.

Hydropower facilities utilize the potential energy of water to generate electricity, with maximum efficiency achieved when there is a significant topographic gradient between reservoir and turbines. Therefore, high dams are typically built in regions with rugged topography, often associated with (frequently combined) erosion, folding or displacement along fault zones, leading to juxtaposed different material properties. At the Enguri Arch Dam in Georgia, extensive limestone formations from the Cretaceous and Jurassic were thrust southward, resulting in a topography difference exceeding 1000 m between the southward-extending Rioni Basin and the contiguous mountain ranges. The reservoir extends about 25 km to the north. There, nearby mountains reach heights of 3000 m and more. As part of the ongoing crustal shortening process, multiple fault systems have emerged, including prominent SW-NE trending thrust faults, steep strike-slip faults, and to a minor extend normal faults. The Enguri valley carves into the surrounding mountains, reaching an elevation of 280 m above sea level at the dam site. These substantial topographic variations between hilltops and valleys establish a variable initial stress field characterized by lateral heterogeneity in both magnitude and orientation. The initial stress conditions were determined using borehole imaging data and hydraulic fracturing tests, while the mechanical properties of the subsurface materials were evaluated using mechanical tests on core samples. The Enguri high-head Dam has a construction height of 271 m and the Jvari-reservoir reaches at full level more than 510 m above sea level. Geodetic GNSS and seismic stations were installed to evaluate the impact of the annual water level changes of about 100 m on the surrounding area. The subsurface information on stress conditions and material properties was used to create an elastic 3D model of the area. The modelling results were compared with field observations to gain a better understanding of the dynamic processes in the area. In a first step the initial stress field was simulated. Loads were applied to simulate the water level changes. Modelled and observed displacements indicate that rising water level causes the west bank to move north-west, while the east bank moves south-east. Furthermore, both banks of the valley show a downward movement. Conversely, when the water level decreases, the effect is reversed. Variations in water level induce changes in the shear stress and changes in Coulomb Failure Stress (ΔCFS) calculated for different fault orientations. They reveal an increased seismic potential during low water levels, aligning with first seismic observations.

The Santiaguito volcanic dome complex in Guatemala consists of four volcanic domes formed within the 1902 eruption crater of Santa María volcano, with only the oldest dome, Caliente, currently active. Caliente is characterized by frequent explosive eruptions, rockfalls, pyroclastic flows, and blocky lava flows. TanDEM-X data enable the generation of high-resolution digital elevation models of complex volcanic terrain. Repeated acquisitions over the same area allow for the detection and quantification of topographic changes associated with volcanic activity. This study investigates elevation and volume changes at Caliente’s southern flank and western crater region from September 2011 to April 2019 using 24 TanDEM-X-derived digital elevation models with spatial resolutions of 6.5 m (N–S) and 4 m (E–W). Between 2011 and 2016, several new lava flows were emplaced on the southern flank, while the crater region experienced a volume decrease of (545±4)⋅103m3. From 2016 to 2019, significant dome growth increased the volume in the crater region again by (354±3)⋅103m3, primarily in the center. Concurrently, volume decreased along the northwestern crater rim, likely due to the 2016 explosive eruption. The average volume output rate over the entire observation period is calculated as 0.18±0.0004m3/s. The results align with previously determined cyclic patterns at Santiaguito volcano and provide a qualitative and quantitative description of the behavioral shift during our period of observation.

Time series of interferometric SAR (InSAR) images offer the potential to detect and monitor surface deformation with high spatial resolution, even for slow deformation processes. However, many different sources contribute to phase changes which are used in InSAR to estimate displacements. Complex displacement mechanisms or strong atmospheric contributions can complicate the separation of these contributions and even cause problems when unwrapping the phase. A preliminary model of expected displacements can support this process but requires information about all involved deformation processes. However, as these processes are often the main subject of the investigation, they are not sufficiently understood in advance. In this contribution, we approach this issue by analyzing InSAR time series results of regions with complex deformation behavior with the established statistical methods of principal and independent component analysis to identify dominant displacement patterns. We study Sentinel-1 InSAR data from 2015 to 2022 above the storage cavern field Epe in North Rhine Westphalia, Germany. Epe displays a spatially and temporally complex surface deformation field, which was described in previous studies as consisting of a linear signal relating to the cavern convergence as well as of seasonal and cavern pressure-dependent contributions. Our resulting displacement components can be clearly separated and appointed to different sources. This is supported by ground truth data and supplemental measurements of cavern pressure levels and groundwater levels. We also find that the previously described linear parametrization of displacements related to cavern convergence is no longer sufficient for longer time series. Our results show that we can obtain source-dependent displacement models from long and complex InSAR time series when using ICA. These can then either be used to refine time series processing or to describe the physical processes causing to the surface displacements with a geophysical source model. Both will be the subject of future investigations.

Time series of interferometric SAR (InSAR) images offer the potential to detect and monitor surface displacements with high spatial and temporal resolution, even for small and slow deformation processes. Yet, due to the nature of InSAR, the interferometric signal can contain a multitude of contributions. Different displacement source mechanisms could superpose each other, signals that are residuals of atmospheric and topographic effects could not be completely removed during processing of the time series or non-coherent noise could exist. Therefore, the criteria for the selection of temporally stable pixels are often rather strict, leading to significant reduction of the spatial resolution density.However, to understand the underlying processes of a deformation field, it is important to extract the displacement signals from the data at the best resolution possible and differentiate signals from different source mechanisms. Furthermore, being able to describe the displacement field as superposition of several simple mechanisms is a possible answer to the general question how the information content from tens of thousands of points each coming with a time series over hundreds of acquisitions can be extracted and comprehended.We address these issues, by determining the dominant displacement signals of different sources in a subset of reliable pixels of InSAR time series datasets with data driven component analysis methods. Subsequently we use models of these signals to identify their displacement patterns in previously not regarded pixels. We utilize the statistical principal component analysis for removing uncorrelated signal contributions and compare different blind source separation methods, such as independent component analysis and independent vector analysis for differentiating between displacements of different origin.We apply our method to a dataset of multiple orbits of Sentinel-1 InSAR time series from 2015 to 2022 above the gas storage cavern field Epe in NRW, Germany. Epe displays a complex surface displacement field, consisting of trends caused by cavern convergence, cyclic gas pressure dependent contributions, as well as ground water dependent seasonal displacements. With our approach, we can successfully distinguish the signals of the different source mechanisms and obtain a dense spatial sampling of these signals. Our results show good agreement with geodetic measurements from GNSS and levelling and show a strong correlation to cavern filling levels and groundwater levels, suggesting causal relations.

At the Enguri Arch Dam, research on methods for a comprehensive monitoring system has been ongoing since 2019. The aim is to identify correlations between different processes and mechanisms, to derive recommendations for the safe operation of the facility. Historical and operational data as well as the results of new measurements will serve as the basis for the analysis. In addition to established methods, new concepts such as the successful testing of GB-SAR for dam deformation monitoring have been implemented and Artificial intelligence (AI) methods will be used.

Since the end of 2022, two ground motion services that cover the complete area of Germany are available as web services: the German Ground Motion Service ( Bodenbewegungsdienst Deutschland , BBD) provided by the Federal Institute for Geosciences and Natural Resources (BGR), and the first release of the European Ground Motion Service (EGMS) as part of the Copernicus Land Monitoring Service. Both services are based on InSAR displacement estimations generated from Sentinel‑1 data. It would seem relevant to compare the products of the two services against one another, assess the data coverage they provide, and investigate how well they perform compared to other geodetic techniques. For a study commissioned by the surveying authority of the state of Baden-Württemberg ( Landesamt für Geoinformation und Landentwicklung Baden-Württemberg , LGL), BBD and EGMS data from different locations in Baden-Württemberg, Saarland, and North Rhine-Westphalia (NRW) were investigated and validated against levelling and GNSS data. We found that both services provide good data quality. BBD shows slightly better calibration precision than EGMS. The coverage provided by EGMS is better than that of BBD on motorways, federal roads, and train tracks of the Deutsche Bahn . As an example, where both services have difficulties in determining the correct displacements, as they cannot be described well by the displacement models used for processing, we present the test case of the cavern field at Epe (NRW). Finally, we discuss the implications of our findings for the use of the products of BBD and EGMS for monitoring tasks.

Radar interferometry (InSAR) has experienced an enormous development during the past decades. Presently, it is the only measurement technique capable of observing ground motion on regional and even continental scale with sufficient point density for highly precise areal monitoring. Thus, it is, besides observation of single objects, predestined for performing wide area surveying tasks. In particular, observation of linear infrastructure (e.g. roads or railways) with InSAR has proven to provide valuable information. First services that monitor foremost linear infrastructure are operative in Italy and Austria. In Germany, no such devoted service on regional scale is currently available. As a starting point for such a service, displacement data from the German Ground Motion Service (Bodenbewegungsdienst Deutschland, BBD) or the European Ground Motion Service (EGMS) that are available for the whole territory of the country, potentially could be used. Factors that determine the usability are the quality of data, the positioning accuracy, the frequency and timeliness of updates and the coverage with measurement points. Regarding coverage, neither BBD nor EGMS are using Distributed Scatterers (DS) for their InSAR analysis of Germany. In order to explore if DS could improve the coverage on roads or train tracks and to provide numbers for coverage of different categories of linear infrastructure (motorways, federal roads, state roads, county roads, train tracks), we evaluate displacement data from different sources. Our investigation is performed for data from the Oberrheingraben south of Freiburg that were processed on the one hand by EGMS and on the other hand by Geodetic Institute Karlsruhe (GIK). The data processed by GIK include DS and are based on essentially the same Sentinel-1 data as the EGMS data. The observed distinct increase of coverage that results from the use of DS may help to justify the additional effort to include DS in the processing of BBD or EGMS for Germany. Furthermore, the obtained numbers will allow stakeholders to better assess the usability of the data. In addition, the results from a stack of TerraSAR-X strip map data gives an impression of what can be achieved with higher data resolution.

Artificially created and oil or gas filled caverns in salt layers are an important component for energy storage. Due to the pressure difference between the interior of the caverns and the surrounding rock, caverns experience constant convergence, that causes significant surface displacements. Monitoring these displacements is not only important for infrastructure health, but also to study the way the volume loss of the cavern translates to the surface. Traditionally, surface displacements are monitored with GNSS and levelling campaigns. However, both techniques usually only offer either good temporal resolution or good spatial coverage. Multitemporal SAR interferometry (InSAR) can provide both and complement traditional geodetic methods but is only slowly becoming popular due to the more complex data processing and interpretation. We want to show that utilizing InSAR can help to understand a complex surface displacement field such as Epe storage cavern field. Epe is Germanys second largest storage cavern field and not only subject to simple linear cavern convergence dependent subsidence. Prior studies found varying cyclic signals that have been connected to injection and extraction cycles of the gas caverns, as well as seasonal displacements induced by groundwater level changes. With InSAR time series of more than eight years of data, we can now observe displacement patterns and gain new insights into the dynamics of the cavern field, that cannot be detected without the dense spatial and high temporal coverage of multitemporal InSAR. We show that even for a long time span, the InSAR estimated surface displacements fit quite well to levelling and GNSS measurements and prove InSAR of equal quality and an excellent addition to traditional surface displacement monitoring methods. Analyzing our results, we find a clear relation of cavern filling levels and shape and amount of subsidence in the cavern field.

Since the end of 2022, two ground motion services that cover the complete area of Germany are available as web services: the latest release of Bodenbewegungsdienst Deutschland (BBD) [1] provided September 2022 by Federal Institute for Geosciences and Natural Resources (BGR) and the first release of the European Ground Motion Service (EGMS) [2] as part of the Copernicus Land Monitoring Service. Both services are based on InSAR displacement estimations generated from Sentinel-1 data that were processed by GAF AG with software developed by Earth Observation Center (EOC), which is part of German Aerospace Center (DLR). It suggests itself to ask, if there is some added value of BBD over EGMS and how well do the two new releases perform compared to other geodetic techniques. For a study commissioned by the surveying authorities of the state of Baden-Württemberg (Landesamt für Geoinformation und Landentwicklung Baden-Württemberg (LGL)), we investigated the performance of BBD and EGMS and validated them against levelling and GNSS data.

The storage cavern field at Epe has been brined out of a salt deposit belonging to the lower Rhine salt flat, which extends under the surface of the North German lowlands and part of the Netherlands. Cavern convergence and operational pressure changes cause surface displacements that have been studied for this work with the help of SAR interferometry (InSAR) using distributed and persistent scatterers. Vertical and East-West movements have been determined based on Sentinel-1 data from ascending and descending orbit. Simple geophysical modeling is used to support InSAR processing and helps to interpret the observations. In particular, an approach is presented that allows to relate the deposit pressures with the observed surface displacements. Seasonal movements occurring over a fen situated over the western part of the storage site further complicate the analysis. Findings are validated with ground truth from levelling and groundwater level measurements.

The satellite positioning service SAPOS, a joint project of the Working Committee of the Surveying Authorities of the Laender of the Federal Republic of Germany, provides correction data that improve the accuracy of GNSS position determination from originally 3 m 10 m to less than 1 cm. For this purpose, a nationwide network of permanent GNSS stations with a mean station distance from 30 km – 40 km archived data since the beginning of 2000. Interferometric SAR, especially Persistent Scatterer (PS) time series analysis, provides a method for spatially dense detection of deformation with an accuracy of 1 cm 3 cm. Unlike GNSS, the location of natural PSs, which are used to create time series of ground displacement from radar images, is not known exactly. The combination of GNSS and SAR interferometry has great potential. To better link the two techniques corner reflectors can be used, which represent artificial PSs. However, installing the corner reflectors, several aspects have to be considered. To avoid interference, there should be no natural PS point within the same and adjacent resolution cell of the Corner Reflector. Similarly, cells should be avoided in which a diffuse signal of high intensity is detected, but no PS is established. For these reasons, preliminary studies at potential sites were carried out as part of a student project in cooperation with the State Office for Geoinformation and Land Development Baden-Württemberg (LGL) and the Surveying and Cadastral Administration Rhineland-Palatinate (VermKV).

Die Festschrift zur Verabschiedung von Prof. Bernhard Heck enthalt 41 Beitrage aus dem Freundeskreis, der Kollegenschaft sowie von ehemaligen Promovierenden. Der Schwerpunkt der Arbeiten liegt auf den Gebieten der Physikalischen und Satellitengeodasie sowie der Geodynamik und spiegelt das vielfaltige Wirken von Bernhard Heck wider. Abgerundet wird die Schrift durch Beitrage zur Ausbildung am Geodatischen Institut des KIT und zur Stellung der Geodasie im gesellschaftlichen Kontext. The commemorative publication in honor of Prof. Bernhard Heck contains 41 contributions written by friends, colleagues, co-workers and former PhD-students. The focus of the scientific articles is on Physical and Satellite Geodesy as well as on geodynamics. It reflects the wide range of academic and scientific research activities of Bernhard Heck. The volume is completed by articles about education at the Geodetic Institute of KIT as well as the importance of Geodesy for society. Umfang: XX, 308 S. Preis: €59.00 | £54.00 | $104.00

TanDEM-X has proven to be an excellent tool to monitor topographic changes during volcanic eruptions. In the present paper, we summarize the results for all volcanoes that we have studied until today and give an overview of the potential of repeatedly generated TanDEM-X DEMs and differencing with respect to the study of active volcanism.