2. If TZ is to the right of CZ, C.E. is East. Formula: True - Right - East.

3. If TZ is to the left of CZ, C.E. is West. Formula: True - Left - West.

You must now remember that what you have is a Compass Error, consisting of both Variation and Deviation. To find the Deviation, the Variation and C.E. being given, is merely to apply the rules already given you under Dead Reckoning. For instance, if you had a C.E. of 10° W and a Variation of 4° E, the Deviation would be 14° W.

Put this example in your Note-Book:

LAT 20h 59m 57s Lat. 4° 55' N Dec. 10° 39' 30" N

Ship heading N 11° W. CB of (.) S 88° E. Variation 10° W. What was the ship's true course and Deviation of Compass on direction ship was heading?

CZ 92° (New compass reading)
TZ 80° (New compass reading)
——
CE 12°
CE = 12° W
Variation 10° W
——
Deviation 2° W
True course being sailed N 23° W or 337°.

Let us now work out some of the following examples:

1. L.A.T. 22h 14m 18s
Lat. 30° 29' S
Dec. 17° 28' 44" N
Ship heading S 84° W
Compass Bearing 44°
Variation 10° W.