Iceberg Detection over Northern Latitudes Using High Resolution TerraSAR-X Images

Kurzfassung

Over northern latitudes, icebergs frequently cross shipping routes and impair marine traffic. To improve ship routing, we propose a novel algorithm that is intended to detect and chart icebergs from Synthetic Aperture Radar (SAR) images provided by the German satellite TerraSAR-X. TerraSAR-X is in a near-polar orbit and fully operational since January 2008. Equipped with an active X-band antenna, it is able to monitor the ocean and frozen waters regardless of cloud cover and darkness, providing a resolution of down to 3 m. Hence, even small icebergs become visible. The proposed algorithm is based on the iterative censoring constant false alarm rate (IC-CFAR) detector, which has proven its usefulness for target detection already. Different from the standard approach, we not only estimate statistical properties of open water backscatter expressed by a probability density function, but also survey in more detail recurring patterns (i.e. waves) building on former studies on wind and sea state retrieval. This allows discriminating icebergs from most false alarms that arise from rough sea and strong winds. Experiments carried out with a series of HH polarized TerraSAR-X StripMap images acquired between 2012 and 2014 confirm that - due to consideration of wave pattern during image processing - the false alarm rate is reduced by factor three. On average, we recorded 0.002 false alarms per km² and a detection rate of 93 %. Since results are output in near real time (NRT), we provide the basis for supporting operational ship routing in remote ice infested areas.