Map Datums and Position
Formats
What are a Map Datum and which
should I use?
A datum is a mathematical model of the Earth that
approximates the shape of the Earth and enables cal-
culations to be carried out in a consistent and accurate
manner. The datum is physically represented by a
framework of ground monuments (i.e. trig. stations)
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 ref-
erence, and the 76CS Plus can be set to match most of
those commonly used.
If you are navigating and comparing the GPS coordi-
nates to a map, chart, or other reference, set the map
datum in the GPS unit to the same datum as the map
to ensure the most accurate navigation.
What is a Position Format and which
should I use?
Your current location can be viewed on the GPS in the
form of coordinates. Since different maps and charts
use different position formats, Garmin GPS units al-
low you to choose the correct coordinate system for
the type of map you are using. The most common for-
mat is latitude and longitude, which is utilized by all
Garmin units.
You may choose to change the position format to use
with other coordinate systems. UTM/UPS (Universal
Transverse Mercator/Universal Polar Stereographic)
is an easy-to-use metric grid 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).
For more information about using paper maps with
your Garmin unit, refer to
Using a Garmin GPS with
Paper Land Maps
, available for download at
http://www.garmin.com/manuals/UsingaGarminGPS
withPaperLandMaps_Manual.pdf.
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PPENDIX
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ORMATS
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