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In a region with magnetic declination of 2°E, the magnetic Fore bearing(FB) of a line AB was measured as N79°50'E. There was local attraction at A. To determine the correct magnetic bearing of the line, a point O was selected at which there was no local attraction. The magnetic FB of line AO and OA were observed to be S52°40'E and N50°20'W, respectively. What is the true FB of line AB?
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- N81°50 ' E
- N82°10 ' SE
- N84°10 ' E
- N77°50 ' E
- N81°50 ' E
Correct Option: C
δ = 2° E
Magnetic FB of AB = N 79° 50' E = 79° 50'
Corrected FB of O A = N 50° 20' = 309°40'
∴ Correct BB of OA = 129° 40'
Observed FB of AO = Observed BB of OA = 552°40' E = 127° 20'
Error = MV – TV = – 2° 20'
∴ correction = 2°20'
TB of FB of AB = N 79°50' E + δ + correction
= N 79°50' E + 2 + 2°20'
= N 84°10' E
