Map Datums and Location FormatsMap Datums are based on a mathematical model of the Earth.What Are a Map Datums?A datum is a mathematical model of the Earth that approximatesthe shape of the Earth and enables calculations to be carried out in aconsistent and accurate manner. The datum is physically representedby a framework of ground monuments whose positions have beenaccurately measured and calculated on this reference surface. Linesof latitude and longitude on a map or chart are referenced to aspecifi c map datum. Every chart has a map datum reference, and youcan set the GPSMAP 376C to match most of those commonly used.If you are navigating and comparing the GPS coordinates to a map,chart, or other reference, set the map datum in the GPS unit to thesame 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 ofcoordinates. Because different maps and charts use differentlocation formats, Garmin GPS units allow you to choose the correctcoordinate system for the type of map you are using. The mostcommon format is latitude and longitude, which is used by allGarmin units.You can choose to change the location format to use with othercoordinate systems in Location field of the Setup tab—Locationsub tab. UTM/UPS (Universal Transverse Mercator/Universal PolarStereographic) are easy-to-use metric grids that are found on mostUSGS topographic quadrangle maps. You can also select one ofseveral other grids, including a user-defi nable grid (for the advanceduser).For more information about using paper maps with your Garminunit, refer to Using a Garmin GPS with Paper Land Maps, availablefor download at www.garmin.com/manuals/UsingaGarminGPSwithPaperLandMaps_Manual.pdf.126 GPSMAP 376C Owner’s ManualAPPENDIX > M AP DATUMS AND LOCATION FORMATS190-00508-00_0C.indd 126 11/6/2006 9:47:48 AM
