Directions are expressed in everyday life as right, left, straight ahead, and so forth. But the question arises, To the right of what? Military personnel require a method of expressing a direction that is accurate, adaptable for use in any area of the world, and has a common unit of measure.

Directions are expressed as units of angular measure, and there are several systems used.

1. The most commonly used unit of angular measure is the degree with its subdivisions of minutes and seconds.

2. Another unit, less frequently used, is the mil (abbreviated m). For the U.S. military Purposes, a complete circle is divided into 6,400 mils. The mil is

Figure 5-21.-True, magnetic, and grid azimuths.

commonly used in artillery, tank, and mortar gunnery. It is convenient for many practical uses because it is approximately one unit of length at a distance (range) of one thousand units.