Compass Terminology


BASE PLATE:  The flat part of the compass; the magnifying lens, map scales, direction of travel arrow, and a hole for the neck cord are in this part.

HOUSING:    The round dial that turns; has orienting lines, orienting arrow, North point, magnetic needle, and is graduated to 360° in 2° increments.

TRUE NORTH:  Actual direction of the North Pole.

GRID NORTH:  The vertical grid lines (Meridians) on a topographical map.

MAGNETIC NORTH: The direction toward which the magnetic needle points (somewhere north of Hudson Bay in Canada).

MAGNETIC VARIATION:  The angle between true north and magnetic north (here it is 17 ˝ degrees East).

GRID OR MAP BEARING:  “Map-to-terrain” bearings.

FIELD BEARING:  Magnetic or compass bearing; “terrain to map.”

“SETTING” THE MAP:  Turning the map so that North is North.

BACK BEARING:  Shooting back to the landmark to see if you are still on the line--turn you and your compass around; point the direction of travel arrow at the landmark; with the bearing degree set, the “south” arrow will be in the North lane if you are still on line.