The angle between the true meridian and the magnetic meridian is MAGNETIC DECLINATION. If the north end of the compass needle is pointing to the east of the true meridian, the declination is said to be east. If the north end of the compass needle is pointing to the west of the true meridian, the declination is said to be west. (See fig. 13-6.)

The magnetic needle aligns itself with the earths magnetic field and points toward the earths magnetic pole. In horizontal projections, these lines incline downward toward the north in the Northern Hemisphere and downward toward the south in the Southern Hemisphere. Since the bar takes the position parallel with the lines of force, it inclines with the horizontal. This phenomenon is the MAGNETIC DIP.

When you have corrected a compass bearing for local attraction, you have a MAGNETIC BEARING. As explained previously, in most areas of the earth, a magnetic bearing differs from a true bearing by the amount of the local magnetic declination (called magnetic variation by navigators). The amount and direction of local declination are shown on maps or charts of the area in a format similar to the following:

"Magnetic Declination 2645W (1968), Annual Increase 11. " This means, if you are working in 1988 (20 years later), the local declination is

To convert a magnetic bearing to a TRUE BEARING, you apply the declination to the magnetic bearing in precisely the same way that you apply local attraction to a compass bearing. If the declination is east, it is added to northeast and southwest magnetic bearings, and it is subtracted from southeast and northwest magnetic bearings. If the declination is west, it is added to southeast and northwest magnetic bearings and subtracted from northeast and southwest magnetic bearings.

When you have a compass bearing and know both the local attraction and the local declination, you can go from compass bearing to true bearing in a single process by applying the ALGEBRAIC SUM of local attraction and local declination, Suppose that local attraction is 6W and declination, 15E. You could correct for local attraction and convert from magnetic to true in the same operation by applying a correction of 9E to the compass bearing.