Finding The Correct Direction (MGRS)

You have learned how to find your location (map coordinates) and how you can use the map scale to determine the distance. The next step is to find the correct direction. These three things will keep you from getting lost.

The top of the map is north, the right edge is east, the bottom is south, and the left edge is west. The direction from one point to another point (either on the map or on the ground) is called an azimuth.

Azimuth

Azimuths are given in degrees in a clockwise direction. Since there are 360 degrees in a circle, your azimuth can be any number up to 360 degrees. Due east is 90 degrees, due south is 180 degrees, due west is 270 degrees, and due north is 360 degrees.

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To get the right azimuth from a map, you have to use a protractor. If your coordinate is 220 850 and you want to find the azimuth to a certain road junction, draw a line from your location to the road junction. Place the protractor on the map and be sure to line it up properly, keeping the cross-center lines of the protractor parallel with the grid lines. The azimuth as shown by the protractor is 223 degrees.

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Suppose you follow the 223 degrees azimuth to the road junction, and then you want to go back to your original location. To do this, you must take a back azimuth. Simply subtract 180 degrees from the first azimuth. Your back azimuth is 223 degrees minus 180 degrees, which equals 43 degrees.

If you cannot subtract 180o from your first azimuth because it is too small, then just add 180 degrees. For example, if your azimuth was 40 degrees, you know that you cannot subtract 180 degrees from it, so add 180 degrees. The back azimuth would be 40 degrees plus 180 degrees, which equals 220 degrees. Remember, a back azimuth goes in the opposite direction from the azimuth.

CAUTION: When converting azimuths to back azimuths use extreme care when adding or subtracting the 180o. A simple mathematical mistake could cause disastrous consequences.

North

The north-south lines on a map give grid north. The compass needle points to magnetic north. Grid north and magnetic north usually have a few degrees difference. Neither points straight at the North Pole—that is called “true north.” However, it is not necessary to know where true north is to avoid getting lost in a combat area.

The difference in degrees for every map between grid north and magnetic north is shown at the bottom of the map. This difference is called the “G-M angle”. The diagram at the bottom of newer maps shows how to change grid azimuths to magnetic azimuths and magnetic azimuths to grid azimuths.

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For example, you aim your compass at a distant tower and get a compass reading of 190 degrees. This is called a magnetic azimuth. The diagram on the map shows that the G-M angle is 9 degrees. To convert the magnetic azimuth to a grid azimuth, add the G-M angle 9 degrees to the compass reading of 190 degrees. This gives you a grid azimuth of 199 degrees. Most times, the G-M angle is so small that you do not have to be concerned with it. It depends on what region of the world you are in. Your squad leader will tell you if the G-M angle is large enough in your area to have to apply it.

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Compass

Use your compass to find or follow an azimuth. The compass arrow points towards magnetic north. The arrow is also attracted by any mass of metal such as a jeep, a truck, your rifle, your helmet, and even electrical power lines. Therefore, to get correct readings when using your compass, avoid any metal objects. To shoot an azimuth, use the center-hold technique. It is faster, easier, and more accurate than the old sighting method.

First, open the compass so that the cover forms a straight edge with the base. The lens of the compass is moved out of the way. Place your thumb through the thumb loop, form a steady base with your third and fourth fingers, and extend your index finger along the side of the compass. Next, place the thumb of your other hand between the eyepiece and the lens, extend your index finger along the other side of the compass and your remaining fingers around the fingers of your other hand, and pull your elbows firmly into your sides. This puts the compass between your chin and your belt.

To measure an azimuth, turn your entire body toward the object, pointing the compass cover directly at the object. Once you are pointing at the object, simply look down and read the azimuth from beneath the fixed black index line. You can even use this method at night.

If you are land navigating, stop occasionally to check the azimuth along which you are moving to keep from going in circles. You can move from object to object along your path of travel by shooting an azimuth to each object and then moving to that object. Repeating this process while you navigate should keep you on a straight path.

It is important to know your compass. The lensatic compass is the most common and simplest instrument used for measuring direction. Your compass is a sensitive instrument and care should be taken in its use and handling.

Your compass can also be used at night. The lensatic compass shown has luminous lines and dots. The bezel ring is a ratchet device that clicks when turned. All of these features are built into the compass to help you set an azimuth and follow it at night. How to keep your compass on course at night takes a little know-how.

 

[Continue to How to Hold a Compass]

**Information adapted from the United States
(U.S.) Army Training Support Centers (TSCs)
Graphic Training Aid (GTA) GTA 05-02-013,
How To Avoid Getting Lost.