If you take a single line of position (LOP), what can you determine?

• A. You know your exact coordinates
• B. You know your speed
• C. You know your heading
• D. You know where you're not

Answer: (D)

With a single line of position you have a locus, a line on the chart that contains all possible positions consistent with the measurement. That line constrains where you could be, but it does not give your exact coordinates, your speed, or your heading. In practice, you use the line to exclude locations off the line, so you know where you’re not. To pinpoint an exact position you’d need a second independent line of position that intersects the first, giving your precise fix.