Search results with incorrect information, duplicate vessels, or duplicate MMSIs and/or call signs can occur. This is generally because:

The following provides answers to problems some users may come across when searching for a vessel.

If a vessel reflags it might require a change in MMSI and call sign to comply with the new flags MMSI and call sign requirements.

If a vessel has a change in ownership the original owner needs to release the call sign and MMSI for the vessel to the new owners. If the original owner does not do this then the vessel may be assigned a new MMSI and call sign.

When searching for a vessel using an IMO number you may find multiple matches which reflect changes to the vessel’s other identifiers over time.

A vessel owner may choose to retain their MMSI and/or call sign after they have transferred ownership of the vessel. They may reuse the MMSI and/or call sign for another vessel. After a period of non-use, MMSIs and/or call signs may also be recycled for new vessels.

This means that in some cases one or more AIS transceivers may broadcast subsequent messages with the same MMSI, but from positions that are physically impossible given required travel times. Starboard marks these with unique vessel IDs to avoid their details being jumbled together.

Information is entered into the AIS transponder by a technician and occasionally this can be done incorrectly.

As above, this may also be related to the reuse of a MMSIs and/or call signs.

Where Starboard has marked a vessel with unique vessel IDs and caused genuine tracks to split into "two" vessels, we mark only the vessel with the most positions as "In [Register]" if a match was made to two vessels with identical MMSIs.