Position Format; Datum - Lowrance GlobalMap 100 Installation And Operation Instructions Manual

Position Format

The GlobalMap 100 can show the position in degrees, minutes, and thou-
sandths of a minute (36° 28.700') or degrees, minutes, seconds, and tenths
of a second (36° 28' 40.9"). It can also show position in UTM (Universal
Transverse Mercator) projection, British, Irish, Swedish, Swiss, Finnish,
New Zealand, and Military Grid.
UTM's are marked on USGS topographic charts. This system divides the
Earth into 60 zones, each 6 degrees wide in longitude.
German, Taiwan, British, Irish, Swedish, Swiss, New Zealand, and Finn-
ish grid systems are the national coordinate system used only in their
respective countries. In order to use these grid systems, you must be in
the respective country. This unit will pick the matching datum for you when
you select the grid. See the Datums section for more information.
The military grid reference system (MGRS) uses two grid lettering
schemes, which are referred to as standard and alternate MGRS on the
GlobalMap 100. Your position and datum in use determines which one to
use. If you use the standard, and your position is off significantly, then try
using the alternate.
Note: When the position format is changed, it affects
the way all positions are shown on all screens. This
includes waypoints.
To change the format, highlight the "Position 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 for-
mat 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.
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