How to Realign a Compass to the Earth's Magnetic Field

Your compass needle will always point to magnetic north. This can cause a problem if you try to navigate without properly aligning your compass to account for the magnetic declination of your area. The Earth's magnetic field is constantly shifting, and the magnetic north to which your compass needle naturally points can be many miles from the true geographic north to which all maps are aligned. A properly aligned compass that compensates for this discrepancy will help ensure that you are traveling in the proper direction according to the map so that you reach the destination you are aiming for.

Things You'll Need

  • Topographical map
  • Orienteering compass
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Instructions

    • 1

      Find the declination value of your location, which in most instances is printed on your topographic map. The declination value is the difference in degrees between magnetic north and geographic north and will be listed as X-degrees east or west. Local ranger stations and commercial outfitters will also typically have knowledge of the current declination values for their area.

    • 2

      Align the orienting arrow inside the compass head with the direction of travel arrow at the top of the compass. When these two arrows are aligned, your compass dial should show a reading of 360 degrees.

    • 3

      Adjust the compass needle. Using the compass key for your orienteering compass, turn the tiny metal screw located on or beneath the rotating compass head until the needle aligns with the declination value. If the declination value is indicated as X-degrees west, add X to 360 degrees, or start from zero to determine the proper setting. If the declination value is indicated as X-degrees east, subtract that value from 360 to determine the proper setting.

    • 4

      Place the compass on the map, and align your orienting arrow and direction of travel arrow with the true north lines printed on your map.

    • 5

      Rotate the map and compass together, keeping the map and compass arrows aligned with each other until the magnetic needle aligns with your compass arrows. You are now facing true north and aligned properly with your topographic map.