Determining The Distance (MGRS)

You can also use your map to measure the distance between two places because maps are drawn to scale. This means that a certain distance on the map equals a certain distance on the earth. This scale is printed at the bottom and at the top of the map (for example, Scale 1:50,000). This signifies that 1 inch on the map equals 50,000 inches on the ground. In fact, any ground distance equals 50,000 times that distance on the map.

NOTE: Always check the scale on your map before trying to measure distance because different maps have different scales.

Two methods by which to determine distance are the—

  • Bar scale method.
  • Pacing method.

Bar Scale Method

There are three different bar scales at the bottom of your map. Use these scales to help convert map distance into miles, meters, or yards. To figure the distance on the ground using the bar scale method, take a ruler (straightedge) or use the edge of a piece of paper and put a tick mark on it at the straight-line distance between your two points. Then put the ruler or paper beneath one of the bar scales and read the ground distance in miles, meters, or yards.

navigation_determining_distance_bar_scales

Estimating the scale between the marks, the bar scale in the figure above shows a ground distance of about 1,520 meters.

Suppose you want to find the distance between point A and point B around a curve in a road (image below). Take a strip of paper, make a small tick mark on it, and line up the tick mark with point A. Align the paper with the road’s edge until you come to a curve, make another tick mark on the paper and on the map, then pivot the paper so it continues along the road’s edge. Repeat this until you get to point B, always following along the road’s edge with your paper. Make a mark on your paper at point B, then go to the bar scales to find the distance.

navigation_determining_distance_bar_scales_curves

Pacing Method

When you have to go a certain distance on foot without any landmarks to guide you, you can measure distance pretty accurately by counting your paces. The average pace is just a little less than 1 meter. The average person uses 116 paces to travel 100 meters.

NOTE: If you find that you do not take 116 paces for 100 meters, determine how many paces you do take by pacing yourself on a known 100-meter distance.

When traveling cross-country, as you do in the field, you will use more paces to travel 100 meters—usually about 148 instead of 116. This is because you are not traveling over level ground and must use more paces to make up for your movement up and down hills. Pace yourself over at least 600 meters of cross-country terrain in order to learn how many paces it takes you to travel an average 100 meters. Be sure you know how many paces it takes you to walk 100 meters on both level and cross-country terrain.

The big problem in pacing is maintaining a straight line. At night, the average person tends to walk in a circle if he does not use a compass. During the day, you should use a compass and steering points (well-defined objects in your direction of travel toward which you may steer). Also, remember to figure only the straight-line distance when you have to walk around an obstacle.

Another problem in pacing is keeping count of the paces taken. One way to keep count is to use pebbles. For instance, suppose you want to pace off 1 kilometer. (One kilometer is 1,000 meters or the distance between two of the black grid lines on your map.) Put 10 pebbles in your right pocket. When you go 100 meters, move one pebble to your left pocket and start your count over. When all 10 pebbles have been moved to your left pocket, you have traveled 1 kilometer. Another way to keep count is by tying knots in a string—one knot per 100 kilometers.

NOTE: 100 meters is approximately 109 yards. If you are using a map that uses miles instead of kilometers, you need to know that there are 1760 yards in a mile.

 

[Continue to Finding the Correct Direction]

**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.