The global digital elevation model (DEM) produced by the TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) mission is an interferometric elevation model with unprecedented quality, accuracy, and coverage. It represents an unedited surface model and artifacts inherent to the interferometric Synthetic Aperture Radar (SAR) acquisition and processing technique are still present. The most prominent artifacts are water bodies appearing with a rough surface in the DEM. Additionally, outliers, voids, and larger data gaps may be present in the dataset. Therefore, DEM editing is crucial for many applications including hydrology or ortho-rectification of remote sensing data. Depending on the field of application different techniques of quality enhancement are required. This paper provides for the first time a comprehensive description of a semi-automatic framework especially developed for the TanDEM-X dataset to edit the high-resolution 12 m DEM with focus on water areas, outlier handling, and void filling. The default configuration parameters of the workflow can thereby be adapted interactively for challenging areas where appropriate. A quality assessment of the edited DEM is done by statistical measures, visual methods as well as by an artifact evaluation.

This paper presents the first comprehensive review on the scientific utilization of earth observation data provided by the German TerraSAR-X mission. It considers the different application fields and technical capabilities to identify the key applications and the preferred technical capabilities of this high-resolution SAR satellite system from a scientific point of view. The TerraSAR-X mission is conducted in a close cooperation with industry. Over the past decade, scientists have gained access to data through a proposal submission and evaluation process. For this review, we have considered 1636 data utilization proposals and analyzed 2850 publications. In general, TerraSAR-X data is used in a wide range of geoscientific research areas comprising anthroposphere, biosphere, cryosphere, geosphere, and hydrosphere. Methodological and technical research is a cross-cutting issue that supports all geoscientific fields. Most of the proposals address research questions concerning the geosphere, whereas the majority of the publications focused on research regarding “methods and techniques”. All geoscientific fields involve systematic observations for the establishment of time series in support of monitoring activities. High-resolution SAR data are mainly used for the determination and investigation of surface movements, where SAR interferometry in its different variants is the predominant technology. However, feature tracking techniques also benefit from the high spatial resolution. Researchers make use of polarimetric SAR capabilities, although they are not a key feature of the TerraSAR-X system. The StripMap mode with three meter spatial resolution is the preferred SAR imaging mode, accounting for 60 percent of all scientific data acquisitions. The Spotlight modes with the highest spatial resolution of less than one meter are requested by only approximately 30 percent of the newly acquired TerraSAR-X data.

This work analyzes the potential synergies between the two German satellites of the TerraSAR-X/TanDEM-X mission and the Spanish PAZ satellite. Since both platforms are almost identical and they were launched in the same orbital plane, comparable images of the same area under the same geometry may be regularly acquired by both systems. This allows the simultaneous exploitation of both missions for building larger time series and improving the revisit time of 11 days for each mission up to 4 or 7 days while combining both. The geometric accuracy and the interferometric performance when combining both sensors are investigated, considering different acquisition parameters and land cover types. For this study several images are acquired over German and Spanish calibration test sites. The results obtained when combining acquisitions from satellites of the TerraSAR-X/TanDEM-X and PAZ missions show no loss of performance with respect to image pairs of the same satellite, indicating that both missions might be exploited synergistically in order to improve current monitoring applications or maybe to allow newer application with tighter requirements in terms of revisit time or temporal coverage. In order to explore all these possibilities, a call for scientific proposals will be jointly opened by the coordinators of the scientific activities of both missions in order to explore the simultaneous exploitation of TerraSAR-X/TanDEM-X and PAZ data.