How to Convert a Grid Azimuth to Magnetic

In land navigation, azimuth is the direction from you to a target location, measured in degrees clockwise from north. Unfortunately, while your map is oriented to grid north, your compass points to magnetic north. In most locations in the world, magnetic north and grid north do not point to the same north pole. Luckily, land navigation maps have a key to tell you the angular difference between the two directions, "the grid magnetic (G-M) angle," so that you can translate between your map and your compass. The G-M angle symbol is in the shape of the letter "V," with a vertical line signifying grid north and an angled line with a barb on its end signifying magnetic north. Your map gives the G-M angle in degrees next to this symbol.

• 1

  Determine what grid azimuth you wish to convert to magnetic, i.e., the direction you wish to walk according to your map, for example, 100 degrees.

• 2

  Subtract the G-M angle from the grid azimuth if you have an easterly G-M angle, i.e. the magnetic line is to the right of the grid north line. Most of North America has an easterly G-M angle. For example, 100 degrees minus 5 degrees is 95 degrees. This is your magnetic azimuth, the direction you want to walk according to your compass.

• 3

  Add the G-M angle to the grid azimuth if you have a westerly G-M angle, i.e. the magnetic line is to the left of the grid north line. For example, 100 degrees plus 5 degrees is 105 degrees. This is your magnetic azimuth, the direction you want to walk according to your compass.