Magnetic declination 

1) Magnetic declination at a place is defined as the angle between the earth’s magnetic axis and the earth’s Geographic axis, and it is denoted by 

.

2) This can also be defined as magnetic declination at a place is the angle between the magnetic meridian and the Geographic Meridian at that place.

3) Magnetic meridian is the vertical plane which is passing through the earth’s magnetic axis.

4) Geographic meridian is the vertical plane which is passing through the earth’s geographic north-south axis.

ABCC' = is the magnetic meridian or vertical plane

                    passing through the earth’s magnetic axis.

 

ABDD' = is the geographic meridian or vertical plane

                     passing through the earth’s north-south

                      geographic axis.