Blue lines denote negative or west declination, and compass in these areas points west of true north.Ĭontour interval in this graph is two degrees. Red isogonic lines denote positive or east declination where the compass points east of true north. The contour lines (green in map) connecting points where declination is 0° are called agonic lines therefore on these lines the above angular difference is zero and the compass points along the field line that goes through true north and magnetic north. Contour lines connecting points of equal magnetic declination are called isogonic lines. Magnetic Declination Chart (Declination Map)īelow is the contour map of the magnetic field declination based on the World Magnetic Model (WMM) 2010 accessed from NOAA. Magnetic declination changes with time as a result of secular variation of the magnetic field, it also undergoes more rapid variations as a result of magnetic activities originating from the sun. You need to adjust for this declination when working with a map and compass.Īs you approach the magnetic north or south pole, there are areas of compass unreliability where the compass starts to behave erratically and eventually becomes unusable. The angle between true north (the line towards geographic north pole) and the direction towards which the compass points (horizontal component of the magnetic field) is called magnetic declination. The images at the bottom of the geomagnetic field section show how the compass needle alings itself with the magnetic field line.

The compass points in the direction of the horizontal component of the earth's magnetic field at that location. Many people state that the compass needle points to magnetic north pole. Home > Education > Magnetic Declination - Magnetic Inclination Magnetic Declination - Magnetic Inclination (Dip) Magnetic Declination

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