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To reduce the error factor between datum, this unit gives you the capability
to select the datum used by the unit when displaying the map. You can
select a new datum from a list or enter a correction offset based on latitude/
longitude.
To change the datum, first press the MENU key three times. Now press the
key next to the “Datum Translations” label. The screen shown below
appears.
There are two boxes on the left
side of the screen. One reads
“Source Datum”, the other is
“Display Datum.” Before chang-
ing the Datum, you need to know
which datum the navigation re-
ceiver supplying position data
to the GlobalMap 2000 is using.
For example, all Lowrance GPS
receivers (including the LGC-1
GPS module) use WGS 84; all
Lowrance Loran-C receivers
use WGS 72.
The display datum box shows the datum currently displayed on the
mapping screen by the GlobalMap 2000. If the display datum is different
from the source datum, the GlobalMap 2000 “translates” the source datum
to the displayed one. This lets you display a map using any datum on the
list on the right side of the screen.
To change either the source or displayed datum, first press the key on the
right side of the screen next to the desired box that you wish to change.
Then press the up or down arrow keys to move highlight the datum you
wish to use. For example, to change the source datum from WGS 84 to
WGS 72, simply press the key next to the “Source Datum” label, then press
the down arrow key until “WGS 72” is highlighted. When the source box
shows the correct datum, press the ENT key. This saves the datum
displayed in the source box.
Once you have the desired datums showing in both the source and the
display boxes, press the CLR key. This unit returns to the mapping screen,
using the datums you specified.
The default for both the source and display datums is WGS 84.