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Press the up or down arrow keys to move the black box to the desired
position format. Press the EXIT key to both select the format and erase
the position format menu.
TRACK HOLDING
When using a GPS receiver at low speeds, it can have trouble determin-
ing your course over ground, or direction you're
travelling. This is due in large part to SA, or
selective availability. SA is small inaccuracies
purposefully put into the GPS satellite's signal
by the government. This cause wide variations
in the track display and other navigation dis-
plays when using the unit at slow speeds.
If you're using the GlobalMap Sport™ without
DGPS at speeds below 10 miles per hour, a
track holding feature begins slowing the up-
date of your course over ground. At 3 mph, it locks the track dispaly to the
last know heading. With DGPS, it begins at 5 mph and locks at 1 mph.
(Note: This only affects the map when it's in the track-up mode. It always
affects the navigational displays.)
To turn the track holding feature off, press the MENU key, then move the
black box to the "GPS Corrections" label and press the right arrow key.
The screen shown at right appears. Press the left arrow key to turn track
holding off. Press the EXIT key to erase this menu.
DATUM
Maps and charts are based on a survey of the area that's covered by the
map or chart. These surveys are called "Datums". Maps that are created
using different datums will show the same latitude/longitude in slightly
different locations.
All datums are named. The GPS system is based on the WGS-84 datum,
which covers the entire world. Other datums may also cover the entire
world, or just a small portion. By default, the GlobalMap Sport™ shows
your position on the map using the WGS-84 datum. However, it can show
your position using one of 99 different datums.
To change the datum, first press the MENU key, then move the black box
to the "GPS Correction" label. Press the right arrow key. Using the up or
down arrow keys, move the black box to the "Select Datum" label. Now
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