USCG Exam PracticePlotting with variation and deviation (T-V-M-D-C)
A navigator observes a bearing to a charted object and records it as a compass bearing of 042°. Deviation for the vessel's current heading is 5°E and variation from the chart rose is 3°W. The navigator wants to plot this as a true bearing on the chart. Which value is correct, and what is the proper procedure?
- A. True bearing 044°; apply only variation because deviation does not affect bearings to fixed objects
- B. True bearing 040°; subtract both easterly deviation and westerly variation using the uncorrecting formula
- ✓ True bearing 044°; correct from compass to true by adding 5°E deviation then subtracting 3°W variationCorrect
- D. True bearing 034°; subtract total compass error of 8° because both errors are applied in the same direction
Why C is correct
To plot a bearing on a chart it must be expressed as a true bearing. Correcting from compass to true (add east, subtract west): 042° + 5°E deviation = 047° magnetic; 047° − 3°W variation = 044° true. Deviation applies to all compass readings taken aboard the vessel, including bearings to fixed objects, not just to courses steered.