Over the universe differ in magnitude from place to place. It is get that many places have the similar value of magnetic components. The lines are illustrated connecting all places on the earth having similar value of magnetic components. These lines make magnetic map.

(i)  Isogonic lines : These are the lines on the magnetic map joining the places of equivalent declination.

(ii) Agonic line: The line which passes by places having zero declination is known as agonic line.

(iii)Isoclinic lines : These are the lines connecting the points of equal dip or inclination.

(iv)Aclinic line : The line joining places of zero dip is known as aclinic line (or magnetic equator)

(v) Isodynamic lines : The lines connecting the points or places having the similar value of horizontal component of earth's magnetic field are known as isodynamic lines.