# Magnetic maps

Magnetic maps (i.e. declination, dip, and horizontal component) over the earth vary in magnitude from place to place. It is found that many places have the same value of magnetic elements. The lines are drawn joining all place on the earth having same value of a magnetic element. These lines form magnetic map.
• Isogonic lines: These are the lines on the magnetic map joining the places of equal declination.
• Agonic line: The line which passes through places having zero declination is called agonic line.
• Isoclinic lines: These are the lines joining the points of equal dip or inclination.
• Aclinic line: The line joining places of zero dip is called aclinic line (or magnetic equator)
• Isodynamic lines: The lines joining the points or places having the same value of horizontal component of earthâ€™s magnetic field are called isodynamic lines.

# Neutral points

A neutral point is a point at which the resultant magnetic field is zero. In general, the neutral point is obtained when horizontal component of Earthâ€™s field is balanced by the field produced by the magnet.