Transcript No Slide Title

CONVERTING BEARINGS
Before converting a grid bearing to a magnetic bearing and vice
versa, there are two things you must do:
GRID
1. Update the magnetic declination
on your map.
MAGNETIC
2. Draw a sketch of the norths and
the bearing you are working with.
a. Draw a zero line for Grid North.
b. Plot the Magnetic North zero
line east or west of Grid North
depending on the declination.
c. Plot a line clockwise from the
appropriate North to represent the
bearing.
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MAG.
DECLIN.
GRID
BEARING
OHP-1
CONVERTING FROM A GRID TO A
MAGNETIC BEARING
When converting to a magnetic bearing, you either add or
subtract the magnetic declination, also called the grid
magnetic angle (GMA).
WEST IS BEST: When the GMA is west of
Grid North, add it to the grid bearing.
EAST IS LEAST: When the GMA is east of
Grid North, subtract it from the grid bearing.
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OHP-2
CONVERTING FROM GRID TO
MAGNETIC
Easterly declination:
GMA
385 E
Grid bearing:
1600 mils
Magnetic Bearing??
Westerly declination:
GB: 3200 mils
GMA 420 W
Magnetic
Bearing??
Mag. Bearing = Grid Bearing - GMA
MB = GB + GMA (West is Best)
MB = 1600 mils - 385 mils (East is Least)
MB = 3200 mils + 420 mils
MB = 1215 mils
MB = 3620 mils
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OHP-3
CONVERTING FROM A MAGNETIC TO A
GRID BEARING
Converting from a magnetic to a grid bearing is done in the same
manner, but with a few important differences.
WEST IS LEAST: When the GMA is west
of Grid North, subtract it from the magnetic
bearing.
EAST IS BEST: When the GMA is east of
Grid North, add it to the magnetic bearing.
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OHP-4
CONVERTING FROM MAGNETIC TO
GRID
Easterly declination:
GMA 385
mils E
MB 5465
mils
Westerly declination:
GMA
385 W
Grid
Bearing??
MB
1954 mils
Grid
Bearing??
GB = MB - GMA (West is Least)
GB = MB + GMA (East is Best)
GB = 5465 mils + 385 mils
GB = 1954 mils - 385 mils
GB = 1569 mils
GB = 5850 mils
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OHP-5