Since the line joining the magnetic poles is titled with respect to the geographic axis of the earth, the magnetic meridian at a point makes angle with the geographic meridian. This angle between the true geographic north and the north shown by a compass needle at which the needle stays in equilibrium in magnetic meridian is called the mag. declination or simply declination.
The declination is greater at higher latitudes and smaller near the equator. The declination in India is small, it being 0º41′ E at Delhi and 0º58′ W at Mumbai. This means a compass needle would deflect towards east by 0 degrees & 41 minute at Delhi & towards west by 0 degrees & 58 minute at Mumbai. As both angles are almost 00, Thus, we can say, at both these places a magnetic needle shows the true north quite accurately.