Originally Posted by goboatingnow
isn't that because class B does necessarily transmit Heading information ,
Looking at: AIVDM/AIVDO protocol decoding
I don't see anything in the protocol preventing Class B from transmitting heading, but there is a '511' 'not available' code.
Now that I think about it more, that probably is the case as most Class B AIS
units don't have access to a compass
(unless N2K connected).
So Furuno's orientation of the triangle on the screen
is based on heading plus they draw an arrow showing COG..?? If heading in missing, IMO, they should use COG for orientation of the triangle. It simply looks stupid to have some targets pointed in the direction of travel and others pointed straight up.
BTW, Class B does the same a Class A except (per the USCG site):
- Has a reporting rate less than a Class A (e.g. every 30 sec. when under 14 knots, as opposed to every 10 sec. for Class A)
- Does not transmit the vessel's IMO number
- Does not transmit ETA or destination
- Does not transmit navigational status
- Is only required to receive, not transmit, text safety
- Is only required to receive, not transmit, application identifiers (binary messages)
- Does not transmit rate of turn information
- Does not transmit maximum present static draught