Garmin GPS 100 - Manual (Page 40)

In place of the speed and track information on line 3, you may want to
calculate the range and bearing from a reference to your present position.
(This information will give you a better understanding of where you are
relative to a known location.)
To calculate range/bearing from a reference waypoint...
· Press the CLR key on line 3 to select the reference waypoint option.
· Enter the reference waypoint name. The GPS 100 will continuously
display range and bearing from the waypoint as illustrated below.
If you have entered the alarm circle of a proximity waypoint (see Section 4.8
on proximity waypoints), you will be informed with the message “PROX
ALARM-PRESS NAV”. When the NAV key is pressed, the Position Page
illustrated above will be displayed with the proximity alarm waypoint already
entered in the reference field for you. The GPS 100 will continually update
the range and bearing from the proximity waypoint to your position on line
3.
If the GPS 100 needs altitude to perform 2D navigation, you will be informed
with the message “NEED ALT - PRESS NAV”. When you press the NAV key,
the Position Page will be displayed as illustrated below:
The last known altitude will be displayed to the right of “ALT:” as illustrated
above. If the altitude is correct, simply press the ENT key with the cursor over
the altitude. Otherwise, enter the altitude of your antenna. (If your antenna
is mounted on a high mast, make sure you add the mast height.)
If your speed is less than 65 knots, you need to enter your altitude only once.
If your speed is 65 knots or greater, the unit will ask you to update your altitude
every 10 minutes with the message “NEED ALT - PRESS NAV”.
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