Automatic ship detection and confidence estimates
About the publication
Report number
17/01317
ISBN
978-82-464-2989-2
Format
PDF-document
Size
2.8 MB
Language
English
The Norwegian Defence Research Establishment (FFI) has been doing research on ship
detection in Synthetic Aperture Radar (SAR) imagery since the late 1980’s, and the Norwegian
Armed Forces have used SAR images operationally since 1998. From the beginning and until
now there has been a growing interest in operational ship detection. There are many key
questions in operational ship detection, and one is confidence levels for ship detection. That
question and other factors related to confidence levels are being looked at in this report.
One way of making confidence estimates is to gather evidence that can support a decision
whether the vessel is a real ship or a false alarm. The ship size, ship-to-sea contrast, morphology
and ship wake detection can be used as pieces of evidence. The incidence angle of the SAR
satellite (e.g. if the satellite looks near-range or far-range) will affect the ability to detect a
vessel at sea. In addition, the latest SAR satellites have the possibility to acquire more images
each with different polarizations. Information about incidence angle and polarization can be
used to improve the confidence estimate.
The algorithms described in this report can be improved over time with more validated data
available. Land based and space based Automatic Identification System (AIS) data should be
used to be able to provide significant input to the algorithms for validation of ship detection in
SAR imagery.
FFI has developed an automatic ship detection tool, AEGIR, which detects vessels in all
polarisation channels. The algorithms described are implemented in AEGIR.