Garmin aera 796 Pilot's Guide - Page 193

Overview GPS Navigation Appendix I APPENDIX I: MAP DATUM AND LOCATION FORMATS 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 chart are referenced to a specific map datum. Every chart has a map datum reference and the aera 795/796 can be set to match most of those commonly used. LOCATION FORMATS Your current location can be viewed on the GPS in the form of coordinates. Since different charts use different location formats, Garmin GPS units allow you to choose the correct coordinate system for the type of chart 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. Several other grids, including a user-definable grid (for the advanced user), are available. Flight Planning Hazard Avoidance Additional Features Appendices Index 190-01194-00 Rev. A Garmin aera 795/796 Pilot's Guide 179