Map Datums And Location Formats; What Are Map Datums And Which Should I Use; What Is A Location Format And Which Should I Use - Garmin GPSMAP 276C Owner's Manual

What are Map Datums and which should I use?

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 (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 specifi c map datum. Every chart has a map datum reference and the GPSMAP
276C 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.

What is a Location 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 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 choose to 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-defi nable grid (for the advanced user), may also be selected.
Appendix
Map Datums and Location
Formats
Map Datums are based on a mathematical model of the Earth.
95