In 1860 the magnetic bearing of a line was n69 270 w with a magnetic declination of 5° 120' e. compute the magnetic bearing of this line today if the magnetic declination is now 7o 360' e. what is the astronomic bearing of this line?

a) N60°30'W

b) astronomic bearing = 299°30'

Explanation:

Given:

Magnetic bearing = N69°270'W

Magnetic declination = 5° 120' E

Now,

True bearing =  Magnetic bearing - Magnetic declination

or

True bearing = N69°270'W - 5° 120' E = 64°150'

also,

The current magnetic declination is 7°360'E

therefore,

The present magnetic bearing = 64°150' - (7°360'E - 5° 120' E )

or

The present magnetic bearing = 64°150' - 2°240' = N60°30'W

Now,

the astronomic bearing of this line = 360° - 60°30' = 299°30'