The horizontal angle which a magnetic meridian makes with the true or astronomic meridian is called the magnetic declination, or magnetic variation. If the north end of the compass needle deflects right of the true meridian, the declination is said to be east (Figure 19.13(a)) and if it deflects to the left of the true meridian, the declination is said to be west (Figure 19.13(b)). Declination varies from place to place and at any station time to time.

Figure 19.13 Magnetic Declination

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