Notes on AIS – Automatic Identification System – JJ Report

Two AIS records, Seaway's course around Motuihe & Browns Island, the 2nd is enlarged near Browns

Notes on AIS – Automatic Identification System – JJ Report
Link for Seeing, Signing & Sharing Petition – http://maritimenz.com/AnnulConvictionGainedByAbuseOfCourtProcess
This is not part of the incident analysis but is included as Mr Bolton requested the AIS data from Seaway during the incident, as with this data, all doubt on position & course would have been removed. He was advised that AIS was not fitted to Seaway at that time so data was not available. However it is also useful to show Seaway’s normal track on a weekend voyage.
AIS is a system for vessels that automatically transmits their position & speed to other vessels & to a shore base in VHF radio range. These positions & data are recorded & plotted at a central base. AIS comes in 2 classes – A & B. Class B is a cheaper & simpler version of the full Class A model. Increasing numbers of smaller vessels such as yachts are fitting class B AIS for safety in assisting by giving data on nearby ships & enabling their own local tracking.
The following are 2 screen shots of a weekend voyage of Seaway taken from a publicly available AIS site produced for academic purposes. They show clearly the path of some voyages of Seaway
subsequent to an AIS system being installed.
The 2nd illustration shows the same shot expanded near Browns Island area. These tracks of a weekend selected at random show actual tracks used by Seaway.
The pattern shown is clear. It indicates a pattern that other vessels have a seamanship expectation that the ferry is likely to follow a similar path. This expectation is normal & seamanlike & allowing for it is expected under collision rules. For example, it is sensible to expect that a Devonport ferry would be going between Devonport & Auckland & other vessels always build this probability into the decision making process.
It also shows that a reasonable seaman on another vessel would expect the ferry to probably trend on this curve to port on other days & to build that into the decision making process when assessing courses to steer. Seaway is always turning to port when heading around Browns Island to Auckland.
Link for Seeing, Signing & Sharing Petition – http://maritimenz.com/AnnulConvictionGainedByAbuseOfCourtProcess

Two AIS records, Seaway’s course around Motuihe & Browns Island, the 2nd is enlarged near Browns
Notes on AIS – Automatic Identification System – JJ ReportAIS3

Showing the same shot expanded near Browns Island area
Notes on AIS – Automatic Identification System – JJ ReportAIS2

Notes on AIS – Automatic Identification System – JJ Report

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