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GPSMAP 176/176C Owner’s Manual 73
MAIN MENU > SETUP TAB
• Heading—lets you select the reference used in calculating
heading information. You can select from Auto Mag Var, True,
Grid, and User Mag Var. Auto Mag Var provides magnetic
north heading references which are automatically determined
from your current position. True provides headings based
upon a true north reference. Grid provides headings based
on a grid north reference and is used in conjunction with the
grid position formats. User Mag Var allows you to specify
the magnetic variation at your current position and provides
magnetic north heading references based upon the variation
you enter.
Enter a magnetic variation.
To enter a user-defined magnetic variation:
1. With the Heading field set to User Mag Var, highlight the
Magnetic Variation field and press ENTER.
2. Use the ROCKER to enter the magnetic variation at your
current position and press ENTER.
To enter a Magnetic Variation manually, highlight
the Heading field, press ENTER, select User Mag
Var and press ENTER again.
WARNING: If User Mag Var is selected, you must periodically
update the magnetic variation as your position changes. Using
this setting, the unit does not automatically calculate and update
the magnetic variation at your present position. Failure to update
this setting may result in substantial differences between the
information displayed on your unit and external references, such
as a magnetic compass.