In: Civil Engineering
True bearing remain constant with time. to obtain declination in 1993 first we need to find out true bearing of that point from given data:
based on current bearings:
True bearing = Magnetic bearing (Current) - Declination (Current)
Note: Here current declination is toward west direction and this declination will be deducted from magnetic bearing.
Magnetic bearing =
In WCB =
Magnetic bearing=
True Bearing = Magnetic bearing (Current) - Declination (Current)
=
=
In 1993 magnetic bearing was and true bearing is same which is
So magnetic declination = magnetic bearing - true bearing
=
=
Magnetic declination in 1993 was .