Fix from two bearings
How to think it through
- 1You take two charted marks with the steering compass: so besides variation you need the deviation for your heading.
- 2Convert the bearings to true (deviation and variation) and draw the line back from each mark.
- 3You are on both lines: the fix is where they cross. Best when the lines cross near 90°.
Worked example
Every step says why you do it, which formula you use, the working and the answer.
A fix from two bearings
Using the steering compass (the fixed one, which has deviation) you take Faro dell'Isola at 212°C and Antenna sul promontorio at 113°C. Convert them to true and plot the fix.
- Faro dell'Isola
- 212°C · 50°06.6′N 001°16.1′W
- Antenna sul promontorio
- 113°C · 50°10.4′N 001°07.5′W
- Variation
- 2°W
- Deviation (on this heading)
- 1°W
True bearing of Faro dell'Isola?
Why: Only true bearings go on the chart: apply deviation and variation to the compass bearing.
Working: 212°C − 3° = 209°T
Answer: 209°
True bearing of Antenna sul promontorio?
Why: Only true bearings go on the chart: apply deviation and variation to the compass bearing.
Working: 113°C − 3° = 110°T
Answer: 110°
Read the fix off the chart, where the two lines cross.
Why: Each bearing is a line you are on; where the two lines cross, that is you.
Working: Fix: 50°11.4′N 001°11.9′W
Answer: 50°11.4′N 001°11.9′W