GPSMAP 392/398/492/498 Owner’s Manual 67
MAIN MENU > SYSTM (SYSTEM) TAB
• Distance, Speed and Elevation—sets the units of measure
for distance, speed, and elevation readouts in Nautical (nm,
kt, ft), Nautical (nm, kt, m), Statute (mi, mh, ft), or Metric
(km, kh, m) terms.
• Heading—sets 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 that are automatically determined
from your current location. True provides headings based
on a true north reference. Grid provides headings based on a
grid north reference (and is used in conjunction with the grid
position formats described on page 70). User Mag Var allows
you to specify the magnetic variation at your current location
and provides magnetic north heading references based on the
variation you enter.
To enter a user-defined magnetic variation:
1. With the Heading field set to User Mag Var, highlight the
heading reference field (immediately to the right), and press
ENTER.
2. Enter the magnetic variation at your current location and
press ENTER.
WARNING: If User Mag Var is selected, you must
periodically update the magnetic variation as your location
changes. Using this setting, the unit does not automatically
calculate and update the magnetic variation at your present
location. Failure to update this setting can result in substantial
differences between the information shown on your unit and
external references, such as a magnetic compass.
Manually enter a
magnetic variation.
