A Copernicus downstream-service for the nationwide monitoring of surface displacements in Germany

Advanced interferometric SAR processing techniques (Persistent Scatterer Interferometry, Small Baseline Subset) are able to detect and monitor various surface displacements caused by e.g. gravitative mass movement, subrosion, groundwater extraction, fluid injection, natural gas extraction. These processes can e.g. cause damage to buildings and infrastructure, affect ecosystems and agriculture or affect the economic use of the geological underground by influencing the hydrogeological setting. Despite the maturity and operational readiness of the PSI technology it is rarely used in operational workflows of the German user community (e.g. from responsible authorities). In order to support the operational use of this technique a Ground Motion Service Germany has been designed by the Federal Institute for Geosciences and Natural Resources (BGR) in collaboration with the user community, land surveying agencies, SME and research institutions. A major outcome of this collaboration is the user request regarding a PSI-WAP (Persistent Scatterer Interferometry Wide-Area-Product) dataset of the entire nation (approx. 360,000 km(2)) based on Sentinel-1 data. For this reason the PSI mapping coverage is increased by mosaicking PSI data products from adjacent SAR data stacks. Several case studies has been performed to demonstrate the design of the service. Within this paper one case study regarding the PSI-WAP technique and the calibration/validation scheme is presented. The pilot study is focusing on the built up of an officially approved PSI-WAP dataset. The study area covers an area of >30,000 km(2) and is located in the Northwest German Basin. This is the first time a PSI-WAP analysis is performed in this area. Several natural processes (e.g. compaction of marine sediments, peat growth/shrinkage) and anthropogenic activities (e.g. natural gas extraction, rock salt mining) are causing surface displacements in the study area. The PSI-WAP analysis is based on six adjacent ERS-1/-2 data stacks covering the timespan from 1992 until 2001. Each data stack consists of 49 to 73 acquisitions. A comparison of the PSI results with thematic data (e.g. cumulated volume of extracted natural gas and location of natural gas fields) indicates that a part of the detected land subsidence is caused by natural gas extraction. To summarize, this paper shows i) the design of the Ground Motion Service Germany and ii) a pilot study to exemplarily demonstrate a PSI-WAP, the calibration/validation scheme and value-added-products. (C) 2017 Elsevier Inc. All rights reserved.