Garmin GPSMAP 76CSx User Manual

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GPSMAP 76CSx Owner’s Manual 
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PPENDIX
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M
AP
 D
ATUMS
 
AND
 L
OCATION
 F
ORMATS
Map Datums and Location 
Formats
What Are Map Datums?
A datum is a mathematical model of the Earth that 
approximates the shape of the Earth and enables 
calculations to be carried out in a consistent and 
accurate manner. The datum is physically represented 
by a framework of ground monuments whose 
positions have been accurately measured and 
calculated on this reference surface. Lines of latitude 
and longitude on a map or chart are referenced to a 
specific map datum. Every chart has a map datum 
reference and the GPSMAP 76CSx can be set to 
match most of those commonly used.
If you are navigating and comparing the GPS 
coordinates to a map, chart, or other reference, set the 
map datum in the GPS unit to the same datum as the 
map to insure the most accurate navigation. .
What is a Location Format?
Your current location can be viewed on the GPS in 
the form of coordinates. Because different maps and 
charts use different location formats, Garmin GPS 
units allow you to choose the correct coordinate 
system for the type of map you are using. The most 
common format is latitude and longitude, which is 
used by all Garmin units. 
You can choose to change the location format to use 
with other coordinate systems. UTM/UPS (Universal 
Transverse Mercator/Universal Polar Stereographic) 
are easy-to-use metric grids that are found on most 
USGS topographic quadrangle maps. You can also 
select one of several other grids, including a user-
definable grid (for the advanced user).