Module 9 - Compass
Variation
Read the compass rose or other current official chart information carefully. A statement such as 2°30′W (2022), decreasing 8′ annually, means the west value reduces by eight minutes each year after 2022. Convert minutes consistently and apply the elapsed whole or proportionate years required by the exercise or planning method.
For August 2026, four years after 2022 in a whole-year classroom calculation, 4 × 8′ = 32′. Subtracting that from 2°30′W gives 1°58′W, commonly rounded to 2°W if the chartwork convention requires whole degrees. State the rounding rather than silently discarding minutes.
East/west is part of the value. For signed working in this course, east is positive and west negative when moving Compass → Magnetic → True. Variation may be east or west, so never assume a nationwide value or direction: derive it for the charted place and date.
- Variation = difference between True North and Magnetic North
- Read reference value, epoch, direction and annual change together
- Do not assume a UK value or direction — update the charted variation for place and date
- Record any rounding and retain the east/west sign
Optional quick check
Section 2 of 5
What is 2°30′W in 2022, decreasing 8′ annually, after four years?
Continue studying Compass
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