Why Do Compasses Show Degrees

If you look at a compass — or a compass app — it will probably be marked in degrees like the one shown below (which is a screen shot of the Apple iPhone built-in compass app). These markings represent what we call azimuth, which is defined so that due north is azimuth = 0°, and the azimuth then increases clockwise. For example, if you start facing due north and then begin to turn to your right (clockwise):

• after one-quarter turn you’ll be facing due east, or azimuth = 90°
• after one-half turn you’ll be facing due south, or azimuth = 180°
• after three-quarters turn you’ll be facing due west, or azimuth = 270°
• after a full 360° turn you’ll be back to facing north, so azimuth = 360° is the same as azimuth = 0°

Using azimuth allows us to describe directions more precisely. For example, it’s easy to ask someone to point to azimuth = 20°, but not so easy to say the same thing just using the terms north, south, east, and west. We won’t need such precise measurements in this book, so we’ll stick to using the basic directions (N, S, W, E), but you may find other uses for azimuth in your life or your career.