It does seem that the compass heading of the ship is now closer to parallel with the canal. One of the things I wonder about (this all comes from AIS data), is that I have observed some ships only have accurate compass headings on marinetraffic and vesselfinder for the 'arrow' of direction when they are underway, at 4-5 knots or more, and other ships such as this one show compass headings when they are at a dead stop.
AIS transmission frequency and message contents are dependent on nav status and speed. Nav status is set by humans. Beyond a certain speed AIS ignores nav status and transmits underway messages at underway frequency. Its been a few years since I've had to read the specs so I dont quite remember the details of what changes in message contents. Im guessing that you are seeing some vessels that havent set an underway nav status.
It depends on the source of heading for the AIS device. If using GPS heading then yes, you need to be underway to calculate heading. If the AIS is using ship heading then it should always be available. The AIS spec is mature but unfortunately not much guidance was given for the installation.
Many ships, and certainly all large oceangoing vessels, transmit both course over ground (direction of motion) and heading (direction the bow is pointed). Sites like MarineTraffic and VesselFinder use the heading to draw the vessels on the map in the correct orientation, but in the vessel details they only display the course over ground as far as I can see.
Inland-only vessels don't always have a gyrocompass or GPS compass, or don't have it connected to the AIS transponder, in which cases they only transmit course over ground and not their heading.
walrus01|5 years ago
tastyfreeze|5 years ago
dnndev|5 years ago
roelschroeven|4 years ago
Inland-only vessels don't always have a gyrocompass or GPS compass, or don't have it connected to the AIS transponder, in which cases they only transmit course over ground and not their heading.
polote|5 years ago