How to Use a Map Declination

Map declination describes the angular difference between magnetic north, which a compass indicates, and other measures of north such as grid north or true north. Depending on the location of the person, the magnitude of the declination changes as you move around the globe. To adjust your direction of travel to true north, adjust the bezel on your compass to indicate true north.

Things You'll Need

  • Compass equipped with bezel
  • Map
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Instructions

    • 1

      Identify the declination on your map. Every map contains the declination either in the lower margin or by a note in the map margin. Be sure to use a very new map, as declination changes a bit every year.

    • 2

      Orient the compass on the map with the compass needle pointing north according to the map. Draw a line along the side of the compass. This establishes the direction of north and south as given by the map.

    • 3

      Adjust the bezel on your compass by the number of degrees declination designated by the notes on the map. Make your adjustment so that the compass needle points in the direction of true north.

    • 4

      Modify your course according to the compass reading. As you travel towards a geographic point on your map, the course you are walking references true north instead of magnetic north or grid north.