Suppose you want to convert an azimuth of 135 to the corresponding bearing. This azimuth is greater than 90 but less than 180; therefore, the line lies in the southeast quadrant. As shown in figure 13-3, the bearing angles are always measured from the north and south ends of thereference meridian. (When solving any bearing

problem, draw a sketch to get a clear picture.) For the azimuth, the horizontal direction is reckoned clockwise from the meridian plane. It is measured between either the north or the south end of the reference meridian and the line in question. When we talk about azimuth in this training manual, however, you must understand that the azimuth is referenced clockwise from the NORTH point of the meridian. The numerical value of this 135 azimuth angle is measured from the north. Therefore, in this figure, the value of the bearing is

The complete description of the bearing then is S45E.

For example, if you want to convert a bearing of N30W into an azimuth angle, you know that the angle location must be in the northwest quadrant. Then, draw an angle of 30 from the north end of the reference meridian because you measure azimuth angles clockwise from the north end of the reference meridian. To compute this azimuth angle, subtract 30 from 360; the result is 330. Therefore, the bearing of N30W is equal to 330 azimuth angle.

The basic method of establishing direction of a survey line or a point is with a surveyors compass. (Notice that on most surveyors compasses, the east and west indicators are in the opposite positions from those of the east and west indicators on a map or chart.) In figure 13-4, an

observer is determining the magnetic bearing of the dotted line labeled Line of Sight. First, the observer mounts the compass on a steady support, levels it, and waits for the needle to stop oscillating. Then, the observer carefully rotates the compass until the north-south line on the card lies exactly along the line whose bearing is being taken.

The bearing is now indicated by the needle-point. The needlepoint indicates a numerical value of 40. The card indicates the northeast quadrant. The magnetic bearing is, therefore, N40E.