Garmin 196 Manuale Utente

Pagina di 168
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 
142 
GPSMAP 296 Pilot’s Guide
A
PPENDIX
 > 
M
AP
 D
ATUMS
 
AND
 L
OCATION
 F
ORMATS