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Map datums and location formats – Garmin GPSMAP 296 User Manual

Page 150

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Map Datums and Location Formats

Map Datums are based on a mathematical model of the Earth.

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 (such as trig. stations) whose

locations 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 296 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, the map datum in the GPS unit should

be set to the same datum as the map to ensure the most accurate

navigation.

What is a Location Format?

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 used by all

Garmin units. You can 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. Several other grids, including a user-definable grid (for the

advanced user), are available.
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/UsingaGarminGP

SwithPaperLandMaps_Manual.pdf

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GPSMAP 296 Pilot’s Guide

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