The following bearing observed in the area where local attraction was suspected determine the correct magnetic bearing if the declination is 3$^\circ$30' east.

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written 6.2 years ago by

saxena_archit • 760

modified 6.2 years ago by

sanketshingote • 100

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Line	FB	BB	Declination
PQ	220$^\circ$30'	41$^\circ$15'	3$^\circ$30'E
QR	260$^\circ$45'	79$^\circ$30'	3$^\circ$30'E
RS	19$^\circ$30'	200$^\circ$	3$^\circ$30'E
SP	100$^\circ$	280$^\circ$	3$^\circ$30'E

The difference of BB and FB of SP is 180O hence station S and P free from local attraction

FB of PQ= 220$^\circ$30’, BB Of PQ= 41$^\circ$15’

FB-BB= 220$^\circ$30’ - 41$^\circ$15’= 180$^\circ$
Observed BB of PQ= 220$^\circ$30’

Correct BB of PQ=220$^\circ$30’- 180$^\circ$=40$^\circ$30’

Observed BB of PQ is 41$^\circ$15’

Error is 40$^\circ$30’- 41$^\circ$15’ = - 0$^\circ$45’
Observed FB of QR is = 260$^\circ$45’

Correct FB of QR= 260$^\circ$45’ - 0$^\circ$45’= 260$^\circ$0’

Correct BB of QR =260$^\circ$0’- 180$^\circ$= 80$^\circ$

Observed FB of QR=79$^\circ$30’

Error is 80$^\circ$ - 79$^\circ$30’ = 0$^\circ$30’
Observed BB of RS = 19$^\circ$30’

Correct BB of RS= 19$^\circ$30’ + 0$^\circ$30’=20$^\circ$00’

Correct FB of RS = 20$^\circ$00’ - 180$^\circ$=200$^\circ$00’

Line	Declination	Corrected		True bearing
		FB	BB	FB	BB
PQ	3$^\circ$30'E	220$^\circ$30'	40$^\circ$30'	224$^\circ$	44$^\circ$
QR	3$^\circ$30'E	260$^\circ$	80$^\circ$	263$^\circ$30'	83$^\circ$30'
RS	3$^\circ$30'E	20$^\circ$	200$^\circ$	23$^\circ$30'	203$^\circ$30'
SP	3$^\circ$30'E	100$^\circ$	280$^\circ$	103$^\circ$30'	283$^\circ$30'

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