On chart 3: a fix from two lights
How to think it through
- 1You are off the coast of chart 3 and take two real lights with the hand-bearing compass.
- 2A hand-bearing compass has no deviation: the bearings are magnetic, and the 6°W variation turns them into true.
- 3From the lights draw both lines out to sea: where they cross, that is you.
Worked example
Every step says why you do it, which formula you use, the working and the answer.
A fix on chart 3: Point Victoria and West Point
With the hand-bearing compass you take Point Victoria light at 033°M and West Point light at 157°M, one straight after the other. Plot the fix.
- Point Victoria (Fl.10s72m23M)
- 033°M · 46°27.8′N 006°15.3′W
- West Point (Fl(2)20s61m19M)
- 157°M · 46°21.2′N 006°14.6′W
- Variation
- 6°W
True bearing of Point Victoria?
Why: Only true bearings go on the chart. A hand-bearing compass has no deviation: from magnetic to true you only apply variation, 6°W on chart 3.
Working: 033°M − 6° = 027°T
Answer: 027°
True bearing of West Point?
Why: Same chart variation: the correction is the same as for the first light.
Working: 157°M − 6° = 151°T
Answer: 151°
Plot both lines from the lights and read off the fix.
Why: Each bearing is a line you are on; where the two cross, that is you.
Working: Fix: 46°24.8′N 006°17.5′W
Answer: 46°24.8′N 006°17.5′W