Question

In 1900, the magnetic bearing of a line was N 25° 30’ W and the magnetic declination was 4° 20’ E. In 2020, the magnetic declination at this location is 1° 15’ E. What is the present magnetic bearing?

CORRECT ANSWER IS N 22° 25’ W

Answer 1

True bearing (TB) is the angle measured from the True North direction.

Magnetic Bearing (MB) is the angle measured from Magnetic North.

Magnetic North is the direction to which the Magnetic needle points.

Magnetic Declination (d) is the difference between True Meridian ( line along true north south direction) and Magnetic Meridian (line along magnetic north south direction).

Magnetic declination can either towards East or towards West.

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In the given question,

In 1900,

MB = N 25˚ 30’ W

     d = 4˚ 20’

True Bearing, TB = MB – d

TB = 25˚ 30’ - 4˚ 20’

TB = N 21˚ 10’W

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In 2020,

Declination, d = 1˚ 15’

As the true bearing of the line does not changes with time, TB in the year 2020 is N 21˚ 10’W

MB = TB + d

MB = 21˚ 10’ + 1˚ 15’

MB = N 22˚ 25’ W

Therefore the magnetic bearing in the year 2020 is N 22˚ 25’ W.

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