How to Adjust a Compass for True North

The navigator depends on a compass to get him accurately from point A to point B. Accuracy, however, relies partly on knowing the direction of the North Pole, or "true north." Instead of true north, however, the magnetized needle of a compass points toward "magnetic north." Geographically, true north and magnetic north do not precisely correspond with one another. Compensating for the difference, known as "declination," allows the navigator to take an accurate bearing from his compass.

Things You'll Need

  • Topographical map
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Instructions

    • 1

      Determine the closest isogonic line to your location. These curved lines run from north to south on your map, with each line marked by a degree. This degree marks the angle of declination in your location.

    • 2

      Rotate the outer dial of your compass to match the angle of declination for your area. The compass dial shows all 360 degrees. If, for example, your angle of declination is 20 degrees, rotate your compass until the 20-degree mark sits between or beneath the compass' two parallel red lines.

    • 3

      Pivot until the compass needle, like the declination mark, falls between the the two parallel red lines.

    • 4

      Observe the fixed arrow beside the needle. The letter N, for “north,” sits directly above the arrow. With the compass dial and needle pointing to the declination mark, “N” indicates true north.