Why do AIS messages not include the rudder angle?
It is deliberately avoided to send the rudder angle. This information does not give an accurate indication of the actual path of the vessel. NOTE: The rudder is just a tool to get the ship to start a turn. Due to shallow water, constellation of propellers, one or two rudders, open or closed skegg, dynamically stable or unstable ship as well as wind direction, the rudder angle could be very ambiguous. E.g. a dynamically unstable ship turning to SB could e.g. need 10 degrees port to avoid a ship to turn fast to starboard. If the rudder angle was sent on the AIS it could confuse an observer an another ship or ashore.
