Garmin GPS 90 Owner's Manual & Reference page 53

The GPS 90' s heading information can be displayed
referencing magnetic north (automatic or user-defined),
true north or calculated grid headings. The default set-
ting is automatic magnetic north, which is suitable for
most applications.
To select a heading preference:
1. Highlight the heading field and press
2. Use the arrow keypad to select a heading preference.
E
3. Press the
To enter a magnetic heading:
. 1. Select the 'user mag' heading and press
2. Enter the degrees of magnetic variation.
E
3. Press the
The map datum field is located just below the posi-
tion format field, and comes with a WGS 84 default set-
ting. Although 104 total map datums are available for
use (see the map datum listing on page 78-79), you
should only change the datum if you are using chart s
that specify a different datum than WGS 84.
To select a map datum:
1. Move the field highlight to the 'datum' field and press
2. Use the arrow keypad to toggle through and select the
desired setting. Confirm the setting by pressing
The next listing available from the setup menu is the
Audio/Display submenu, which provides access to
screen contrast, backlighting and tone settings. The GPS
90 features adjustable screen contrast for optimum view-
ing in any condition. The screen contrast is set by using
an on-screen bar scale.
To set the screen contrast:
1. Highlight the 'Contrast' field and press the
L R
2. Use the and
desired contrast and press the
E
key to confirm the selection.
key to confirm the magnetic variation value.
keys to adjust the bar scale for the
E
key.
.
E
.
E
.
E
.
E
key.
Setup Menu
Heading,
Datums &
Screen Contrast
The GPS 90 comes
with the latitude and
longitude position for-
mat and WGS 84
map datum as the
default settings.
Only change the map
datum if the charts
you are using specify
a different map
datum in the legend.
WARNING!
Using the wrong
datum can seriously
effect the accuracy of
your GPS. Always set
the GPS to the same
datum indicated on
the charts you are
currently using.
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