Why would an event be removed from Skylight?
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There may be instances when an AIS-based event that had previously been displayed in Skylight, or was available via API, is no longer visible. As a near real-time system, Skylight displays the most up-to-date information available at the time. However, as additional updated AIS data is received or information processes are run, Skylight may learn that the event did not ultimately meet the requirements. In these rare instances, the event is removed from Skylight.
Vessel(s) involved in an event and later classified as equipment (buoy)
Skylight is designed to show events involving vessels. For example, a Standard Rendezvous shows where two vessels, transmitting AIS, have traveled in proximity at approximately the same speed. To avoid showing instances where gear that is transmitting AIS is involved in a Standard Rendezvous with its vessel, Skylight runs a daily process to identify and classify equipment.
Skylight has a machine learning model that is run once daily to identify vessels that are actually equipment and re-classify them. If that former vessel was involved in an event before the buoy service ran, then an event would display in Skylight:
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The above event was viewed in Skylight on approximately 2022-10-27 T18:35:00 GMT which is before the buoy service was run for the day. The above Standard Rendezvous was visible on the Skylight map and in the downloaded data file. The Vessel Details Screens for each of the above ‘vessels’ would have also shown the Standard Rendezvous events. Once the buoy service was run however, the above vessels were correctly classified as ‘equipment’ and the event removed from Skylight
A vessel that has been classified as equipment will be viewable in the Vessel Details Screen, but there will be no events associated with the vessel after the buoy service is run since those events have been removed from Skylight.
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Dark Rendezvous marked as Duplicate
A vessel cannot be involved in a Dark Rendezvous and Standard Rendezvous at the same time. However, it’s possible that in Skylight a Dark Rendezvous is generated prior to a Standard Rendezvous being created for a vessel. Once the Standard Rendezvous is generated, the system will go back and mark the Dark Rendezvous as a duplicate and the event will no longer be available in the system.
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Out of Order AIS messages
One common reason an event is removed from Skylight is additional AIS data is received out of order and Skylight ‘learns’ the event did not actually meet the requirements. This happens most frequently for Potential Dark ActivitiesAlthough rare for most events, because of the nature of Potential Dark Activities, it is more likely that additional AIS data will come in out of order and change these events.
In the greatly simplified example below, we can see how this might happen. There are four AIS position messages in the below diagram:
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