( iii ) Horizontal Component of Earth ’ s Magnetic Field ( H ) If B is the intensity of earth ’ s magnetic field then horizontal component of earth ’ s magnetic field H = B cos δ
It acts from south to north direction . Vertical component of earth ’ s magnetic field V = B sin δ
∴ B = √H 2 +
V 2 and tan δ = V / H
Angle of dip is zero at magnetic equator and 90 ° at poles . Magnetic Meridian A vertical plane passing through the magnetic axis is called magnetic median . Geographic Meridian A vertical plane passing through the geographic axis is called geographic meridian . Magnetic Map
Magnetic map is obtained by drawing lines on the surface of earth . which passes through different places having same magnetic elements .
The main lines drawn on earth ’ s surface are g1 en below
( i ) Isogonic Line A line joining places of equal declination is called on isogonic line .
( ii ) Agonic Line A line joining places of zero declination is called an agonic line
( iii ) Isoclinic Line A line joining places of equal inclination or dip is called an aclinic line ,
( iv ) Aclinic Line A hne joining places of zero inclination or dip is called an aclinic line .