Garmin gpsmap 96 用户手册

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A datum is a mathematical model of the Earth which 

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 (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 reference and the GPSMAP 96/96C 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 or chart to ensure the most accurate 

navigation.

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. On most models, you can 

choose to change the position 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. Several other grids, 

including a user-definable grid (for the advanced 

user), can also be selected

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