Current affects the accuracy of a running fix. Consider, for example, the situation of an unknown head
current. In Figure 000a, a ship is proceeding along a
coast, on course 000 ° speed 00 knots. At 0000 light A
bears 000°, and at 0000 it bears 000°. If the earlier bearing line is advanced a distance of 0 miles (00 minutes
at 00 knots) in the direction of the course, the running
fix is as shown by the solid lines. However, if there is a
head current of 0 knots, the ship is making good a speed
of only 00 knots, and in 00 minutes will travel a distance of only 0 0/0 miles. If the first bearing line is
advanced this distance, as shown by the broken line, the
actual position of the ship is at B. This actual position
is nearer the shore than the running fix actually plotted.
A following current, conversely, would show a position
too far from the shore from which the bearing was
measured.