Knowing how to use a lensatic compass is a useful skill. While experienced backpackers and hikers may use a GPS unit as the primary instrument for orienteering, they often carry a compass as back up. The lensatic compass is one of several types of compasses that are available. The reliability and ease of use of the lensatic compass are reasons why it is the compass of choice by the United States military.
You will need:
- Lensatic compass
- Gain familiarity with the primary parts of the compass: the cover, base, sighting wire, sighting slot, lens, floating dial, bezel ring and thumb loop. Unlike some compasses, a lensatic compass' entire floating dial moves rather than just a compass needle. The arrow printed on the floating dial points to magnetic north and there is a printed scale from zero to 360 that denotes degrees. Military lensatic compasses have two printed scales: an outer scale in black lettering for mils and an inner scale in red lettering for degrees. The lens, from which the compass gets its name, is used to read the scale to determine a bearing or azimuth while sighting the compass on a distant object used as a reference point.
- The lensatic compass should be held level so that the floating dial can pivot freely. The compass can be held in two ways, the center hold technique or compass to cheek technique. The latter method is preferred because it produces the greatest accuracy.
- To use the compass to cheek technique, open the compass, placing the cover containing the sighting wire in a vertical position. Place the rear sight in a 45 degree position. Place a thumb in the thumb ring and hold the compass next to your cheek with the sighting notch at eye level. Using your other hand to support the hand holding the compass is a good technique to help hold it steady.
- To determine an azimuth to a fixed reference point, look through the sighting notch at the sighting wire. Your entire body should be turned until the sighting wire and notch sight are lined up on the fixed reference point. Look down through the lens at the degree scale and read the bearing.
- To determine which direction to go to follow an azimuth derived from a contour map, look down through the lens at the degree scale while slowly turning the entire body until the desired degree is read. Look through the sighting notch and align the sighting notch and sighting wire on a distant fixed reference point. Using the distant fixed reference point as a guide while walking will keep a person on the desired bearing.