Something is “subsiding” in the state of Denmark - Operational prospects for nationwide subsidence mapping with Sentinel-1

Synthetic Aperture Radar Interferometry (InSAR) has proven to be a highly valuable tool for deformation monitoring applications, and with the emergence of the operational Sentinel-1 mission, the expectations have further increased. However, the technique is also notorious for being challenging, both in implementation and in interpretation. As such, it has mainly been applied in an opportunistic manner - stacks of archived data were processed in batch over specific areas of interest, results would be somehow validated, and reported to the end-user.Due to lack of a stable and reliable SAR data source, it has so far been very hard to build an operational large-scale system for nationwide InSAR deformation monitoring.The Sentinel-1 constellation will bring a paradigm shift to the field with its operational characteristics: mission configuration, acquisition planning, and data distribution policy. However, operational workflows are still to be designed and deployed. State-of-the-art processing algorithms might be considered ready, but other components of the operational chain are still to be profiled if not designed from scratch. Moreover, an important factor for a nationwide mapping system is dissemination of the results to a broader audience than the one consisting of InSAR domain specialists.The objective of this contribution is to, as far as possible at this early stage, address the following questions and/or identify the bottlenecks, from the national-scale perspective:How to integrate algorithmic state-of-the-art in a single processing system?How to operationally deploy the re-defined state-of-the-art?How to validate results?How to communicate results to non-InSAR communities?These questions will be addressed through a case study for the country of Denmark. Specifically, a strategy for development of a nationwide Sentinel-1 InSAR deformation mapping system will be discussed. Denmark is a good case for a first assessment, both due to its size, and due to the expected signal characteristics. Moreover, the proposed map product will be periodically updated and will be of a different resolution for urban and non-urban areas. The availability of reliable in-situ measurements on both local and national scale therefore will over time allow for reliable validation.Initial results will be presented and will serve as basis for a discussion on how to communicate and streamline a portfolio of subsidence products to end users, which is a challenge in itself. We will conclude with a discussion on remaining open questions regarding how to address these issues as a community.This contribution will focus mainly on the overall system level, rather than on algorithmic details.