Thomas Hahmann

Potential for High Resolution Systematic Global Surface Soil Moisture Retrieval via Change Detection Using Sentinel-1

The forthcoming two-satellite GMES Sentinel-1 constellation is expected to render systematic surface soil moisture retrieval at 1 km resolution using C-band SAR data possible for the first time from space. Owing to the constellations foreseen coverage over the Sentinel-1 Land Masses acquisition region-global approximately every six days, nearly daily over Europe and Canada depending on latitude-in the high spatial and radiometric resolution Interferometric Wide Swath (IW) mode, the Sentinel-1 mission shows high potential for global monitoring of surface soil moisture by means of fully automatic retrieval techniques. This paper presents the potential for providing such a service systematically over Land Masses and in near real time using a change detection approach, concluding that such a service is-subject to the mission operating as foreseen-expected to be technically feasible. The work presented in this paper was carried out as a feasibility study within the framework of the ESA-funded GMES Sentinel-1 Soil Moisture Algorithm Development (S1-SMAD) project.

Automatic Extraction of Water Bodies from TerraSAR-X Data

Medium resolution SAR satellite data have been widely used for water and flood mapping in recent years. Since the beginning of 2008 high resolution radar data with up to one meter pixel spacing of the TerraSAR-X satellite are operationally available. The improved ground resolution of the system offers a high potential for water detection. However, image analysis gets more challenging due to the large amount of image objects that are visible in the data. Water body detection methods are reviewed with regard to their applicability for TerraSAR-X data. Flood detection approaches for rapid disaster mapping are presented in this paper.

Strategies for the Automatic Extraction of Water Bodies from TerraSAR-X / TanDEM-X data

Medium-resolution SAR satellite data have been widely used for water and flood mapping in recent years. Since the beginning of 2008 high-resolution radar data with up to 1 m pixel spacing of the TerraSAR-X satellite are operationally available. Due to the improved resolution of the sensor more details of the Earth’s surface become visible. A number of different appearances of water bodies in TerraSAR-X data are shown that are relevant for a general water mapping concept. Existing water body detection approaches that have been applied to medium-resolution SAR data are reviewed with regard to their applicability for TerraSAR-X data. As a complementary mission to TerraSAR-X the launch of TanDEM-X is planned for October 2009. The data of both satellites will be used to generate a global DEM (Digital Elevation Model) with an interferometric data acquisition concept. As a byproduct to the DEM data set a global water mask will be derived from the SAR data. The concept for this water detection process within the TanDEM-X project is introduced in this paper.

Cartographic Representation of Dresden’s Historical Development by Projecting a Movie onto a Solid Terrain Model

On the occasion of the 800th anniversary of the first mention of the city of Dresden (Germany) a new exhibition for the local City Museum was designed. The intention of the exhibitions concept was to use modern and innovative exhibits to attract a broad audience. A key element of the exposition is a 2.00 m by 1.50 m solid terrain model of the Dresden Elbe valley. A film, which shows the development of the depicted region since the year 8000 B.C. is projected onto the terrain model by a video projector and the help of a tilted mirror. This true 3D installation is one of the first of its kind worldwide. It facilitates much more thematic flexibility than terrain models without changing illumination. Both the terrain model and the film result from a cooperation of the City Museum of Dresden with the Institutes for Cartography and for Software- and Multimedia-Technology of the Dresden University of Technology. The scale of the solid terrain model is 1:16,250. It is four times vertically exaggerated to improve the perceptibility of small terrain features for the visitor. The projected film is a FlashMX animation, for which several tenths input data layers were prepared with the GIS software ArcGIS and the vector graphic software Freehand. Input data for both the solid terrain model and the animation were Laserscanning DEM data and ATKISDGM/- DLMdata. A major challenge of the terrain model construction was the reconstruction of the primordial terrain. As the input data showed the contemporary situation of the terrain a significant number of visible anthropogenic terrain changes, such as bridges, railway lines, motorways and man-made riverbeds had to be removed. An iterative semi-automatic approach was developed, which cuts relevant areas from the data and using a linear TIN interpolation that filled the data holes afterwards. The filtered data set was cut into a polyurethane pattern plate by using a Portatec milling machine by the Institute for Production-Technology of the Dresden University of Technology. In a stepwise process an accuracy of 1/100 mm in the three dimensions x, y and z was reached. Afterwards the solid terrain model was varnished with a special white colour, for which previous tests had shown optimum reflection behaviour.