How to identify a ship-to-ship operation (STS)


What are the parameters to look for when identifying a ship-to-ship operation?

For example, how close do ships need to be located to be considered for STS? For how long do they have to stay together? Does it matter if they are facing in the same direction? How do we differentiate an actual STS from the background noise (a.k.a. just two unrelated ships standing close to each other).

Thank you

Excellent questions! Ship-to-Ship (STS) operations are identified by a combination of factors. Let me break them down for you:

  • Proximity: Ships in an STS operation typically are very close together, often within 50-200 meters. The specific distance may vary based on the size of the ships and the nature of the operation.
  • Duration: STS operations often last several hours to a few days, depending on the volume of cargo being transferred. A quick meet-up is unlikely to be an STS operation.
  • Orientation: Ships in an STS operation are often positioned parallel to each other, or “alongside,” to facilitate the safe transfer of cargo. However, this is not a hard rule and the orientation can change due to operational requirements or changing weather and sea conditions.
  • Activity: The presence of additional support vessels, booms, hoses, or lines between the ships are strong indicators of an STS operation. Also, the observed movement of the ships can give clues. For instance, the ships may drift together maintaining a constant distance, which is a good indication of an STS operation.
  • AIS Data: Automatic Identification System (AIS) data can provide further clues. For instance, changes in the ships’ AIS status or course/speed that align with the other indicators mentioned above can suggest an STS operation.

To differentiate an STS from two unrelated ships standing close, look for these factors in combination. If multiple signs point toward an STS operation, it’s likely one is occurring.

However, these are just general guidelines. Each operation may have its own unique factors, so experience and expert analysis are crucial for accurate identification.

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Ship-to-ship (STS) operations involve the transfer of cargo between two vessels positioned alongside each other, primarily at sea. For an operation to be considered STS, the ships typically need to be in close proximity, often within 50 meters or less. The duration of their proximity is indicative, usually spanning hours depending on the cargo volume, while their orientation (facing the same direction) facilitates the transfer. Differentiating genuine STS from unrelated ships requires analyzing the behavior and patterns of the vessels, such as parallel positioning, consistent distance, and prolonged interaction.