A compass is an instrument used to determine direction in fire control work. An azimuth compass is graduated/marked with a full circle of 360 degrees called an azimuth circle. Compass components include a magnetic needle that always points to magnetic north, a graduated circle for laying off angles from true north, and a sighting line for extending a line of sight while following a course of direction. The north end of the needle is marked with a small arrow.
Reading the compass and sighting
1. Always hold the compass level and firmly against the body to keep it still.
2. Determine which direction is north by moving to get the north needle to the correct position, magnetic north.
3. To determine the direction of an object, hold the compass and align the direction of the travel arrow with the object.
4. Read the azimuth where the index line meets the 360°dial. Look along the sighting line and then, by raising the eyes, extend the line of sight.
5. Take note of one or more objects, such as a tree or a rock, along the line of sight. Walk to the most distant object noted along the line of sight, and take another sight with the compass.
The compass direction can also be read off a map, by drawing a straight line between the initial point and the point of destination. Place the compass on the map so the orienting lines on the 360° dial point to north on the map. Read the compass on the map.