Satellite Imaging for Maritime Surveillance of the European Seas

Surveillance for ships on the sea poses particular challenges for spaceborne imaging sensors: small targets need to be detected, wide areas need to be surveyed, and both targets and background are anything but stationary. The incidental, snap-shot satellite images find their application niches - among the existing set of technologies for ship monitoring - mostly by alerting to the presence of unknown targets and in surveying outlying areas. The main applications in the European seas cover fisheries control, pollution control and maritime border security, although (in 2007) operational use is still sporadic. Synthetic Aperture Radar (SAR) is the sensor of choice, because it enables detection of a wide range of ships under a wide range of conditions and over wide swaths. High-resolution optical sensors can provide additional information on ship classification, which is still difficult for SAR. Their narrow swaths, however, mostly limit their use to predetermined locations. Clutter from the sea surface hinders detection of the smallest ships, especially at high sea state, leading to the concepts of false alarms and less than 100 % detection probability. For many applications these drawbacks can be kept within acceptable limits by proper choice of the swath width / resolution / polarisation combination. Satellite sensors may also image ship wakes, from which information on ship speed and heading can be gleaned. Crucial to operational use is the ability for automatic analysis. This is relatively well developed for ship detection in SAR images, less well for classification and wake analysis in SAR images, and quite immature for optical images.JRC.G.4-Maritime affair