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90 iQue 3600a Que Applications Guide
Map Datums and Location
Formats
Generally speaking, the default Map Datum and
Location Format suit most users’ needs.
What is a Map Datum and which one
should I use?
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 (such as
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.
Find the map datum reference on the paper chart you
are using. Set the Map Datum to match the map
datum used by your chart.
What is a Location Format and which
one should I use?
Your current location can be viewed on the GPS in the
form of coordinates. Since 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 utilized by
all Garmin units.
You may change the location format to use with
other coordinate systems in Location Preferences.
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 select several other grids, including a
user-definable grid (for the advanced user).
APPENDIX > MAP DATUMS AND LOCATION FORMATS