Dead‑reckoning (DR) is the practice of estimating a vessel’s present position by projecting its last known position using course, speed, and time. In coastal navigation, DR is often refined by using bearings taken on known landmarks, which creates lines of position (LOPs) that intersect at the vessel’s estimated location.
A transferred position line (TPL) is a special LOP derived when two bearings are taken from two distinct, known points (A and B) to the unknown vessel. By “transferring” one bearing to the other point, a straight line is drawn on which the vessel must lie. The intersection of this transferred line with the second bearing’s line gives the most probable position.
Mathematically, each bearing defines a line in a plane using the point’s coordinates (latitude = y, longitude = x) and the bearing angle measured clockwise from true north. Solving the simultaneous equations of the two lines yields the transferred position line’s crossing point, which is the estimated vessel position.
theta_B = bearing from point B (rad)
t_A, t_B = scalar distances along each bearing
What is a transferred position line in navigation?
How do you calculate a transferred position line?
Why is dead-reckoning important in maritime navigation?
What are lines of position (LOPs) used for in navigation?
How does a transferred position line differ from other lines of position?
Can you use transferred position lines in open sea navigation?
What tools are needed to calculate a transferred position line?
Results are for informational purposes only and do not constitute professional advice.