Garmin GPSMAP 496 Owner's Manual (for North America) - Page 128
Location Sub Tab, Location Format Sub Tab, Map Datum Sub Tab, Selecting a Different Heading Reference
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Main Menu > Setup Tab Location Sub Tab Refer to the "Appendix" of this guide for more information about location formats and map datums. Also visit the National Imagery and Mapping Agency at www.nima.mil for more information on grids and datums. Location Format Sub Tab Changing the Location Format coordinates the system in which a given location reading is shown. The default format is latitude and longitude in degrees, minutes, and thousandths of a minute (hddd°mm.mmm). Map Datum Sub Tab Datums are used to describe geographic locations for surveying, mapping, and navigation and are not actual maps built in the unit. The default setting is WGS 84. The unit automatically chooses the best datum based on your chosen position format. WARNING: Selecting the wrong map datum can result in substantial location errors. You should only change the position format if you are using a map or chart that specifies a different position format or map datum or want to use a format you are familiar with.When in doubt, use the default WGS 84 datum for best overall performance. Selecting a Different Heading Reference You can select from Auto Mag Var, True, Grid, and User Mag Var. Auto Mag Var provides magnetic north heading references that are automatically determined from your current location. True provides headings based on a true north reference. Grid provides headings based on a grid north reference (and is used in conjunction with the grid position formats). User Mag Var allows you to specify the magnetic variation at your current location and provides magnetic north heading references based on the variation you enter. Enter the magnetic variation of your current location in the Magnetic Variation field if you have selected User Mag Var for the heading. WARNING: If you select User Mag Var, the unit does not automatically calculate and update the magnetic variation at your present location. You must update the magnetic variation as your location changes. Failure to update this setting can result in substantial differences between the information shown on your unit and external references, such as a magnetic compass. 120 GPSMAP 496 Owner's Manual