Oliver Lang

Velocity map of the Thwaites Glacier catchment, West Antarctica

Abstract The two-dimensional surface velocity of Thwaites Glacier, West Antarctica, was mapped with 23 ascending- and 22 descending-orbit European Remote-sensing Satellite synthetic aperture radar (ERS SAR) interferograms (time range 1995–2000). The velocity map covers 175 500 km2 from the Amundsen Coast to the southern turning point of the satellite orbit and comprises >80% of the Thwaites catchment. Relative velocity errors are <10% except for rare regions (about 5% of the total area) of unfavorable look geometry. Six individual tributaries were identified; their center-line velocities increase from 0 at the catchment boundary to ~0.3 km a–1 when they join the main glacier trunk. On the main trunk, velocity increases to ~1.8 km a–1 at the grounding line and 3.6 km a–1 on the floating tongue. As at neighboring Pine Island Glacier, no strong longitudinal velocity gradients are found except near the grounding line. Within expected error bounds, the flow pattern appears temporally stationary, i.e. flowlines agree with the delineation of flow suggested by the pattern of velocity magnitude. A potential temporal shift of tributary boundaries must consequently be <4.4 m a–1.

Combined use of TerraSAR-X and RADARSAT-2 data - A study of a virtual constellation

The objective of this project is to investigate the potential of the complementary use of TerraSAR-X and RADARSAT-2 data. Both satellites carry second generation SAR sensors capable of multiple acquisition modes like ScanSAR, Stripmap and Spotlight as well as multi-polarization options [1][2]. A systematic combined data use has clear advantages for many applications, for example an improved revisit of an area of interest (AOI), the availability of near coincident dual frequency data acquisitions and the potential for cross queuing of the two sensors. A problem which constrains the complementary usage of both data sources is the fact that both satellites are operated independently. As a consequence, users encounter difficulties at joint acquisition planning with an optimum combination of imaging modes. A detailed understanding on how to best utilize two independent spaceborne SAR systems in combination is therefore required.

Development of Operational Applications for TerraSAR-X

In the course of the TerraSAR-X mission, various new applications based on X-Band Synthetic Aperture Radar (SAR) data have been developed and made available as operational products or services. In this article, we elaborate on proven characteristics of TerraSAR-X that are responsible for development of operational applications. This article is written from the perspective of a commercial data and service provider and the focus is on the following applications with high commercial relevance, and varying operational maturity levels: Surface Movement Monitoring (SMM), Ground Control Point (GCP) extraction and Automatic Target Recognition (ATR). Based on these applications, the article highlights the successful transition of innovative research into sustainable and operational use within various market segments. TerraSAR-X’s high orbit accuracy, its precise radar beam tracing, the high-resolution modes, and high-quality radiometric performance have proven to be the instrument’s advanced characteristics, through, which reliable ground control points and surface movement measurements are obtained. Moreover, TerraSAR-X high-resolution data has been widely exploited for the clarity of its target signatures in the fields of target intelligence and identification. TerraSAR-X’s multi temporal interferometry applications are non-invasive and are now fully standardised autonomous tools to measure surface deformation. In particular, multi-baseline interferometric techniques, such as Persistent Scatter Interferometry (PSI) and Small Baseline Subsets (SBAS) benefit from TerraSAR-X’s highly precise orbit information and phase stability. Similarly, the instrument’s precise orbit information is responsible for sub-metre accuracy of Ground Control Points (GCPs), which are essential inputs for orthorectification of remote sensing imagery, to locate targets, and to precisely georeference a variety of datasets. While geolocation accuracy is an essential ingredient in the intelligence field, high-resolution TerraSAR-X data, particularly in Staring SpotLight mode has been widely used in surveillance, security and reconnaissance applications in real-time and also by automatic or assisted target recognition software.

Monitoring human activity with high resolution SAR and optical imagery - a synergistic approach

Illegal traffic by off-highway vehicles (OHV) damages the salt crusts of Salton Sea Playa (California, USA) which then impacts air pollution and advances ground erosion. To mitigate the environmental impact of these threads a traffic management plan has been implemented which includes the monitoring of vehicle related disturbances on the Playa. This pilot study assesses the feasibility whether the application of Coherence Change Detection (CCD) technique to very high resolution Synthetic Aperture Radar (SAR) and optical imagery can be used to identify and to quantify OHV traffic. While the impacts on the interferometric coherence are well described, e.g. by atmospheric effects and temporal decorrelation, a quantitative interpretation of the observed signatures in the context of surface changes is still not fully understood. As a consequence, the feasibility of using CCD as a sensitive tool to evaluate subtle surface changes is limited. In this paper we describe a ground truth experiment at Salton Sea Playa and the corresponding analysis of CCD results and high resolution optical image stacks, which have been acquired as a synergistic data source. Goal is to provide a methodical scheme of CCD signatures in relation to known ground disturbance. The recommendations from this pilot study will inform how spaceborne monitoring methodologies can be used in the playa traffic management strategy and how a potential monitoring service should be implemented.

Integration of colorized single-pol SAR data into optical image mosaics

Satellite image mosaics are commonly used for large-scale mapping purposes. Perpetual cloud cover may prohibit the mapping with electro-optical satellite imagery within a reasonable time interval, e.g. in tropical areas. In these cases, the additional use of SAR data can help to complement the image of the earth surface, as cloud-independent spaceborne SAR data has been proven to be a valuable thematic and topographic mapping source [1]. An effective way to realize an integrated image mosaic is the colorization of high-resolution SAR imagery by applying statistical filters and the adaptation of these false colors with respect to an optical reference. The creation of SAR images with a land-cover related color scheme has been shown before [2]. But generally, the resulting images have no relationship to the color impression of an optical scene. The motivation of the technique described in this paper is • to create automatically colour classified products directly from single polarized SAR images • to create seamless mosaics from colored SAR images • to mosaic colored SAR images with electro-optical imagery

Kurzfristige Verbrauchsmaßnahmen für Ottomotoren

Im Hinblick auf die ACEA-Selbstverpflichtung stellt sich immer mehr die Frage, wie die CO2-Zielwerte noch erreicht werden konnen. Masnahmen wie eine Vergroserung der Dieselmarktanteile stosen an die Grenzen des wirtschaftlich sinnvoll Machbaren. Deshalb ist es nicht verwunderlich, dass die Entwicklungsschwerpunkte wieder starker auf den Ottomotor mit seinen langst nicht ausgeschopften Potenzialen fokussiert sind. Im Folgenden werden einige bei der FEV Motorentechnik entwickelte Masnahmen zur Optimierung der Motormechanik und -thermodynamik sowie Applikationsstrategien zur Verbrauchsreduzierung diskutiert, die kurzfristig in die Serienentwicklung einfliesen konnen.

Ventiltriebsvariabilitäten für moderne Ottomotoren

Variable Ventilsteuerungen zur Verbesserung des Drehmoment- und Verbrauchsverhaltens beim Ottomotor werden zunehmend in Serienmotoren eingesetzt. Ein wesentliches Entscheidungskriterium fur die Markteinfuhrung ist neben Marketingaspekten das Kosten-Nutzen-Verhaltnis der unterschiedlichen Systeme. Im Folgenden werden einige bei FEV Motorentechnik entwickelte und erprobte Ventiltriebskonzepte vorgestellt. Neben diesen Anwendungen wird der Einsatz der Variabilitat im Ventiltrieb bei einem Motor mit kontrollierter Selbstzundung sowie bei einem aufgeladenen Motorkonzept diskutiert.