How to Adjust for Declination
- The difference between true north and magnetic north is known as the magnetic declination or variation.
- If magnetic north is west of true north—as is the case throughout the Northeast—it’s a west declination. If east, then it’s an east declination.
- To convert from a true bearing (one determined from a map, for example) to a magnetic bearing (what your compass shows), add a west declination or subtract an east declination.
- A mnemonic can help keep this straight in your head.
- “Empty Sea, Add Water” is shorthand for “MTC, Add W,” which stands for “Map to Compass, Add West.”
- “From map to field the proper yield is east is least and west is best.” This phrase translates to: “From true to magnetic, subtract an east declination and add a west declination.”
- To convert from magnetic to true, simply reverse the formula.
Labels: Compass, Maps, Navigation
