High Resolution 3D Earth Observation Data Analysis for Safeguards Activities

This paper provides an overview of the investigations performed at DLR with respect to the application of high resolution SAR and optical data for 3D analysis in the context of Safeguards. The Research Center Jülich and the adjacent open cut mines were used as main test sites, and a comprehensive stack of ascending and descending TerraSAR data was acquired over two years. TerraSAR data acquisition was performed, and various ways to visualize and analyze stacks of radar images were evaluated. Building height estimation was performed using a combination of ascending-descending radar images, as well as height-form-shadow and height-from-layover. A tutorial on building signatures from SAR images highlighted the sensor specific imaging characteristics. These topics were particularly relevant in safeguards activity with a “small-budget” as only a single image – or a couple - were employed. Interferometric coherence map interpretation allows the detection of traffic on dirt roads. Digital surface models (DSM) were generated from TanDEM-X interferometric data and from optical VHR data. Sub-meter Worldview-2 and GeoEye-1 data was processed into highly detailed DSM with a grid spacing of 1 m, showing building structures. 3D change and volume detection was performed with both optical and radar DSMs. The TanDEM-X DSMs proved useful for volume change detection and computation in mining areas, and DSMs generated from optical satellite data show details on the building level. Virtual 3D fly-throughs were found to be a good tool to provide an intuitive understanding of site structure and might be useful for inspector briefing

L-band Synthetic Aperture Radar: Current and future applications to Earth sciences

International audienc

EO-ALERT: NEXT GENERATION SATELLITE PROCESSING CHAIN FOR RAPID CIVIL ALERTS

In this paper, we provide an overview of the H2020 EU project EO-ALERT. The aim of EO-ALERT is to propose the definition and development of the next generation Earth observation (EO) data and processing chain, based on a novel flight segment architecture moving optimised key EO data processing elements from the ground segment to on-board the satellite. The objective is to address the need for increased throughput in EO data chain, delivering EO products to the end user with very low latency

Towards an Urban DEM Generation with Satellite SAR Interferometry

The mapping of urban areas is a claimed task for many management applications, such as urban development monitoring, urban climate studies, and renewable energy surveys. Airborne data are widely used at this purpose for the generation of Digital Elevation Models (DEMs). LiDAR (Light Detection And Ranging) is a mature technology for obtaining DEMs in urbanized environment. Spaceborne Synthetic Aperture Radar (SAR) is on the contrary not largely exploited due essentially to the lack of suitable data. In fact, an essential prerequisite for a successful exploitation of SAR data finalized to urban reconstruction is a resolution capable to map the desired target. A second one, but not less important, is the absence of temporal decorrelation in between the two SAR acquisitions, or, in other words, an interferometric bistatic configuration. The TanDEM-X mission, started in June 2010, has as primary objective the generation of a global DEM following the high standard accuracy HRTI-3. The X-band sensors employed for the mission allow an accurate building mapping, hence accomplishing the first prerequisite. Additionally the mission constitutes the first bistatic SAR interferometer in space, letting to a faithful surface reconstruction free of atmospheric and temporal decorrelations. The acquisition mode used to achieve the HTRI-3 requirements is the stripmap one, with a final spatial DEM resolution of 12 meters. This resolution does not assure an accurate mapping of dense metropolitan areas, nevertheless semi-urban and industrial areas are well mapped as shown with a validation made using reference airborne data over Munich (Germany). The mission foresees however experimental spotlight acquisitions finalized to the generation of higher resolution DEMs following the HRTI-4 standards with a 6 meters spatial resolution. Considering this resolution, a denser urban mapping becomes then possible. The first example of urban experimental high-resolution DEM is shown over Las Vegas (USA). The processing chain adopted for the interferometric DEM generation, also called Raw DEM, is built in the Integrated TanDEM-X Processor (ITP). Although the chain is highly optimized in a global scale, some modifications are necessary for the purposes of the paper. In particular, the spectral shift filtering, the coregistration, the interferogram generation and the phase unwrapping processing steps are redesigned towards an optimal configuration for the local municipal zone to map. More in detail, the range spectral shift and the phase unwrapping stages are enabled or disabled depending on the scene configuration; the coregistration stage is configured through its patches size and density and the multi looking requested to reduce the phase noise is set to an optimal value controlled by the actual application. Examples over Munich, with different configuration parameters and applications, are provided. The limits of an interferometric SAR city modelling are also introduced and analyzed in detail. The major restriction for a correct DEM generation is intrinsic to the SAR viewing geometry with issues like layover and shadow. Their effects in the Raw DEM, basically consisting in false heights, are analyzed and the road to overcome these problems, based on the adoption of tomographic techniques, is introduced. Acquisitions with different geometries planned to solve geometric difficulties are also scheduled in the TanDEM-X mission but still not available. This paper analyzes a strategy for the generation of urban DEMs, now possible also with satellite SAR interferometry, exploiting the potentials offered by the TanDEM-X mission