Collecting Military Compasses


MKIII Prismatic Marching Compass Instructions for Use


The following simple steps will introduce you to the techniques of direction finding using the compass for map reading.

  1. Hold the compass level and steady in both hands close to your eye with your thumb through the loop. The lid must be open and standing vertical with the prism turned over to the reading position.
  2. Look through the sighting slit on top of the prism and line up the hairline on the glass in the top lid. At the same time, observe through the eyehole of the prism the reading on the compass dial. The prism may be focused on the dial by moving the thumb loop up or down, until a clear picture on the dial appears.
  3. Turn your head slowly, keeping the compass close to your eye until the object you require a reading is in line with the lubber line on the lid, and the sighting slit above the prism. Note the reading on the dial. Make sure you are not carrying or standing near to any metal objects, which could affect the compass reading.
  4. In order to use the compass to set a map turn the Index ring (glass bezel on top of the compass) until the reading over the black line by the compass lid hinge is the same as that viewed through the prism. Tighten the clamp screw on the side of the compass to prevent the ring turning.
  5. Open the compass lid fully and place the compass on the map with the thumb loop pointing out from the compass. The notch on the prism guard and the white line on the thumb loop should be laid along the line of the direcfion of travel, with the lid towards the destination.
  6. Turn the map with the compass on it until the North South Grid lines on the map coincide with the North on the compass dial and the North on the index glass.
  7. Your positlon is somewhere along the line that passes through the object. By taking a bearing on another object and repeating the stages 1 to 6, your position will be where the two lines from the objects intersect.

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