Which DR rule states to plot a new DR position every course change?

• A. Plot a new DR position at least every hour on the hour
• B. Plot a new DR every course change
• C. Plot a new DR every fix or running fix
• D. Plot a new course line from each fix

Answer: (B)

The key idea is updating the dead reckoning (DR) position whenever the vessel changes course. DR is your estimated current location based on the last known position, plus the speed and direction you’ve been traveling. If you turn, the path you’re actually following diverges from what the DR line would predict if you kept the old course. To keep the DR plot accurate, you establish a new DR position at the moment of the course change using the new course and speed from that point, and then continue estimating from there along the new track.

Waiting to update at fixed times (like every hour) can let error grow when turns occur. Plotting DR at every fix or running fix isn’t the standard DR control rule you’re being tested on here, and drawing a new course line from each fix isn’t the DR update action you’re asked to apply.