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Navigating Magnetic Declination

This document discusses how to convert between true and magnetic bearings when given declination. It explains that when declination is west, the magnetic bearing is corrected to true by adding the declination amount, while an eastern declination is corrected by subtracting. It provides the mnemonic "west is best, so add; east is least, so subtract" and notes that conversions may require adding or subtracting 360 to keep the result between 0 and 360 degrees.

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Cesar Del Castillo
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22 views3 pages

Navigating Magnetic Declination

This document discusses how to convert between true and magnetic bearings when given declination. It explains that when declination is west, the magnetic bearing is corrected to true by adding the declination amount, while an eastern declination is corrected by subtracting. It provides the mnemonic "west is best, so add; east is least, so subtract" and notes that conversions may require adding or subtracting 360 to keep the result between 0 and 360 degrees.

Uploaded by

Cesar Del Castillo
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Dealing with Declination


Example declination diagram
2
Declination WEST
TN
MN
10
o
W
Magnetic north is 10 degrees west of true north
To correct a magnetic bearing (e.g. 97) to true,
We need to rotate clockwise to correct
So declination is ADDED to the
Magnetic bearing
WEST IS BEST, SO ADD
97 +10 =107
For True to magnetic, do the opposite (SUBTRACT)
Declination EAST
TN
MN
10
o
E
Magnetic north is 10 degrees east of true north
To correct a magnetic bearing (e.g. 97) to true,
We need to rotate counter-clockwise to correct
So declination is SUBTRACTED from the
Magnetic bearing
EAST IS LEAST, SO SUBTRACT
97 10 =87
For True to magnetic, do the opposite (ADD)
3
Quick solution
Remember:
1. START WITH THE MAGNETIC BEARING
2. WEST IS BEST ADD: EAST IS LEAST
SUBTRACT
3. NOTE THAT YOU MAY GO OVER 360, IF SO
J UST SUBTRACT 360 FROM RESULT
4. TO START WITH TRUE NORTH BEARINGS,
DO THE OPPOSITE

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