Why does a vessel report it's speed as 102.3 in AIS
The AIS specification for SOG (Speed over ground) shows that 102.3 knots is reported when the vessel speed is unavailable. So for some reason the vessel is not transmitting it's speed in it's AIS messages. This could be a technical issue on the vessel.
Speed over ground in 1/10 knot steps (0-102.2 knots)
1 023 = not available, 1 022 = 102.2 knots or higher
In Spire Vessels API and Messages API we return the values as received. We have reports that some other AIS providers take the decision to report the unknown speed value of 102.3 as zero. Technically this is wrong and while appearing correct when the vessel is in port, would not be correct when the vessel is moving or at sea.
For clarity to customers we have changed our reporting slightly in the new platform Spire Maritime 2.0 that will replace Vessels API when launched late Q3 2021.
Maritime 2.0 reports reports SOG values of 102.3 as null because several users experienced confusion from the reported value.
This is what Maritime 2.0 reports.
"collectionType": "TERRESTRIAL", "heading": 358, "speed": null, "timestamp": "2021-08-19T09:36:21.582Z"
Compared to what is rpeorted in Vessels API
"speed": 102.3, "rot": -1.0, "collection_type": "terrestrial", "timestamp": "2021-08-19T09:30:24+00:00"
If you require further help supporting the data provided by Spire then please raise a request for support here https://spire.com/developers/support/