The earth's magnetic field is approximately like that of a giant magnetic dipole, whose axis is inclined roughly `20^@` west of the axis of rotation of earth which is the geographic N-S direction. The strength of earth's magnetic field is of the order of `10^-4 tesla`. Three magnetic elements of earth are: Magnetic declination `(theta)`, magnetic inclination or magnetic dip `(delta)` and horizontal component (H) of earth's magnetic field. Magnetic declination is the small angle between magnetic axis and geographic axis at a place. Magnetic dip at a place is the angle, which the direction of total strength of earth's magnetic field (R) makes with a horizontal line in magnetic meridian. If H is horizontal component and V is vertical component of earth's magnetic field, then `H=Rcos delta`, `V=Rsin delta` and `R=sqrt(H^2+V^2)`. At a place on the surface of earth. H is of the order of `3*3xx10^-5tesla`.
Magnetic declination is