Ship traffic monitoring may be performed using satellite SAR data. The advantage with the SAR sensor is the all weather and day/night imaging capability. However, the SAR backscatter contrast between a vessel and the surrounding sea state may be small in high wind conditions and at small incidence angles. The present and future SAR satellites will have the capability of imaging the earth surface with several incidence angles, and with dual-polarimetry (HH/HV, VV/VH or HH/VV). The SAR ship/clutter contrast may threrefore be increased by applying different polarisation combinations, or using higher incidence angles. We have shown that geocoded ENVISAT ASAR images in the coastal region of Norway can be used to gain experience in the combined use of satellite SAR and an automatic identification system (AIS) for ship traffic monitoring. There are plans for placing AIS systems onboard satellites. It will then be possible to fuse the information from satellite SAR with those from satellite (or ground-based coastal) AIS and thereby identify all the detected ships within a SAR image. This data fusion will enable us to develop further knowledge about SAR backscatter properties from vessel types that may not be detected so well using the SAR data only. On the other side, it will be possible to pin-point those ship candidates that do not carry an AIS system, and thereby take appropriate security or rescue actions.
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