The TanDEM-X Global Water Body Layer

Abstract

The interferometric SAR dataset acquired by TanDEM-X to generate a global Digital Elevation Model, covering at least twice the complete Earth's mass, represents a unique data source to derive geo-information products at a global scale. In the bistatic TanDEM-X system, characterized by the absence of temporal decorrelation, the interferometric coherence adds valuable information to the common amplitude images, typically acquired by SAR systems. Using the interferometric coherence of TanDEM-X acquisitions as the main input, we are in process of generating a global Water Body Layer (WBL). This paper reports on the developed activities for this purpose. The proposed approach takes into account the geometric properties of SAR acquisition scenes, in order to mitigate the effects of geometric distortions, such as shadow and layover, and to improve the discrimination between water bodies and vegetated areas characterized by low coherence. The resulting WBL represents an enhancement of the current Water Indication Mask delivered within the TanDEM-X DEM products. Taking benefit from the two global coverages of TanDEM-X data, it is possible to determine the minimum and maximum areas of extent of the different water bodies. At a local scale, it is even possible to monitor the water bodies extension variability and their seasonality. On coastal regions, at a local scale and by means of time series, it is possible to monitor the evolution of the coastal line over time.