The military lensatic compass is the standard issue navigational tool for overland travel by members of the military when operating on land. The compass is made up of a base with a ruler on the left side to be used in measuring distances on a map. The cover (with a vertical slot visible when opened) has a thin metal wire running vertically that is used to sight on distant objects when walking. The compass section is comprised of a floating dial with degrees from North (360), clockwise to East (90) to South (180) to West (270) printed around the circumference of the dial. The clear cover over the floating dial has a luminous line that can be matched up to the degree/direction that you plan to move towards. This direction is referred to as an azimuth.
Understand the terms. An azimuth is a mathematical term denoting the direction in which you are traveling. The opposite direction is referred to as a back azimuth. To find your azimuth, you need a map with grid lines (preferably a 1:50,000 scale), protractor (clear, flat tool with degrees marked on its edge to help plot courses on a map) and your compass.
Lay the map out flat on a table or the ground and find the legend which will show you where North is denoted on the map. This arrow is not pointing towards actual North, it is just showing you where North is with respect to the map. With your compass you will be able to find out which way is true North. Now, find out where you are on the map. You can use surrounding land formations or masses (mountains, forests or rivers) to try and determine where you are in relation to the map. Draw a line from where you are to where you want to go.
Place the protractor on the map so the top of the protractor is pointing towards North on the map. Place the center of the protractor where the drawn line crosses a vertical line on the map. Where the drawn line meets the edge of the protractor is a degree number. This is your azimuth. Let’s say that your line crosses the 270-degree point on the protractor. If you lay your compass on the map (lined up with north on the map), and look at where the needle is facing north you will know which direction north is. Now you need to orient (turn) the map to the actual north heading. Now both your compass and your map are oriented to the North. Take the 270 degree measurement from the protractor and rotate the compass so the luminous line is over the 270-degree mark on the floating dial. Now turn the dial so the line on the clear cover is over the north-pointing arrow on the floating dial. Keep that set there so you will always know which way is north if you get lost as you are moving. Your direction (270) is set by the red luminous dial. That is the line you want to make sure stays over the 270 so you will continue to move in the right direction. To help in maintaining your direction, every one hundred feet or so, you should stop and use the metal sighting strip to guide you towards a fixed object (such as a tree, hill or rock formation). This will ensure you are maintaining the proper direction. Once you are at the fixed object, look at your compass again, making sure you are still moving in the right direction, find another object and repeat.
Know how to return. When you get to your location and want to return to where you started, you simply use a back azimuth. To find your back azimuth, add 180 degrees to your previous azimuth (if it is less than 180 degrees) or subtract 180 degrees if the azimuth was more than 180 degrees. Follow this new azimuth back to your previous location.
Care should be taken when handling a military compass. Try to keep from using it around large metal objects and anything that is magnetic. This will cause a false North reading and could cause you to get lost. Keep the military compass in a protective case so it doesn’t get dirty or the casing over the floating dial doesn’t crack.
Things You'll Need
- Military compass
- Map (with grid lines)
Misusing a military compass can be dangerous if you don’t understand the proper procedures for calculating an azimuth and back azimuth.
- Map image by Stephen VanHorn from Fotolia.com