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Verify vessel positions

Verifying a vessel position is key to understanding if the vessel is trustworthy in their position reporting.

VAKE uses Sentinel 1 (SAR) and Sentinel 2 (Optical multispectral imagery) to verify a vessel position. We do it by analyzing if a capture overlaps with the reported AIS position. You can easily see all verified positions of a track in the dynamic menu (right menu).


Optical captures​

Sentinel 2, being medium resolution optical captures, are the best to view details on the captures. You can visually identify that a vessel is the vessel in question.

Benefits of Sentinel 2:

  • True-color imagery – intuitive visual understanding. Surrounding elements can be spotted easily.
  • 13 spectral bands – supports advanced analysis. Images can be used with our Clearview-feature, to e.g. find a vessel through vessel signatures when going dark.
  • High spatial resolution – up to 10 meters per pixel in key bands (RGB, NIR).

Drawbacks of Sentinel 2:

  • Cloud-dependent – can be completely blocked by cloud cover or haze.
  • No night imaging – only works in daylight.
  • Lower revisit frequency – every 5 days with both satellites, but useful pixels might be less due to clouds.

Radar​

Sentinel 1, being a Synthetic Aperture Radar, gives black & white images with lesser resolution. However, it has a clear advantage in some cases:

Benefits of Sentinel 1:

  • All-weather operation - penetrates clouds.
  • Day & night operation – works in darkness.
  • High temporal resolution – revisits every 6–12 days per satellite (2 satellites = every 6 days).

Drawbacks of Sentinel 1:

  • More complex data – radar data (backscatter) is less intuitive, and has lesser resolution than sentinel 2.
  • Lower spatial resolution – typically 10–20 meters per pixel. However, to get more confidence in the visual verification of a SAR-detection, one can e.g. measure the length of the vessel at hand to make sure that the vessel actually is the vessel of interest. This can be done through e.g. Sentinel-hub.
  • No color imagery – no natural or multispectral views. Makes it more difficult to understand surrounding elements for an untrained eye.