If GPS is unreliable, which method could be used to determine position using two known landmarks?

• A. Use a radar fix.
• B. Bearings to two known landmarks and lines of position.
• C. Use dead reckoning.
• D. Consult the nautical almanac.

Answer: (B)

When GPS isn’t reliable, you can fix your position by using bearings to known landmarks and plotting lines of position. Each bearing to a landmark defines a line on the chart where you could be located relative to that landmark. By drawing two such lines—from two different known landmarks—you obtain their intersection, which is your estimated position.

For example, measure the bearing from your vessel to two distinct landmarks whose charted positions you know. On the chart, draw the line that corresponds to the reciprocal bearing from each landmark. The point where those two lines cross is your position. The accuracy improves when the landmarks are well separated in angle; if they line up, the intersection becomes less precise.

Radar fix and dead reckoning are useful methods in other scenarios, and celestial navigation uses the almanac and stars, but for determining position from two known landmarks without GPS, bearings and lines of position is the standard approach.