53
To change the position format, highlight either the
“Position Format” or the “Alternate Format” label
on the “GPS Setup” menu, then press the right
arrow key. A screen similar to the one at right
appears. Press the up or down arrow keys to
select the desired format. Press the EXIT key to
erase the position format 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, your position shows using the
WGS-84 datum. However, it can show your position using one of 191
different datums.
To change the datum, first press the MENU key,
then highlight the “GPS Setup” label and press
the right arrow key. Now highlight the “Select Da-
tum” label. Finally, press the right arrow key again.
A screen similar to the one at right appears.
The WGS-84 label is highlighted. To change it,
simply press the up or down arrow keys to high-
light the desired datum, then press the ENT key.
This selects the datum and erases the select datum menu.
A list of the datums used by this unit is in the back of this manual.
Set PCF Offset
Another method used to make your display match a chart or map is called
“PCF” or Position Correction Factor. This unit gives you the capability to
move or offset the position shown on the display to match one on the
chart. The unit will add this offset to all position and navigation displays at
all times.
Remember, the position error on any radio navigation system is very dy-
namic and the PCF offset should never be used in an attempt to cancel
the error.
