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Compasses are marked according to two major systems. Easiest to use, and standard with the United States armed forces, is the azimuth system, by which bearings are specified in degrees up to a circle of 360°, in a direction clockwise from north. Compasses graduated on that system usually have the case marked counterclockwise, so that if the north—south line of the case is directed toward the object, the north end of the needle will read directly in degrees of azimuth. Thus a northwest bearing would be given as 315°. Most civilian surveying in the United States is based upon four segments of the circle, graduated respectively from north and south 90° in each direction to east and west; a northwest bearing is given as north 45° west. |
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