Garmin GPSMAP 188C Sounder User Manual download pdf (Page 77)

GPSMAP 188/188C Sounder Owner’s Manual 71

MAIN MENU > UNITS TAB

• Heading—selects 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 upon

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. Use the ROCKER to 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 displayed on your unit and external

references, such as a magnetic compass.

Manually enter a

magnetic variation.

• Distance, Speed and Elevation—allows you to select the

units of measure for distance, speed, and elevation readouts

in nautical (nm, kt, m), statute (mi, mh, ft), or metric

(km, kh, m) terms.

• Depth—allows you to select the units of measure for depth

in feet (ft), fathoms (fa) or meters (m).

• Temperature—allows you to select the units of measure for

temperature in Fahrenheit (°F) or Celsius (°C).

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Garmin GPSMAP 188C Sounder User Manual Page 77