Garmin GPS 72 - Manual (Page 47)

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Introduction
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Reference
‘ Map Datum’ — Datums are used to describe geographic positions for surveying, map-
ping, and navigation and are not actual maps built in the unit. Although there are over
100 datums available to choose from, you should only need to change the Map Datum
if you using a chart or paper map that specifi es a different datum in the legend. See
Appendix D for a list of Map Datums.
WARNING: Selecting the wrong map datum can result in substantial posi-
tion errors. When in doubt, use the default WGS 84 datum for best overall
performance.
‘ North Reference’ — Let’s you select the reference used in calculating heading informa-
tion. You can select ‘Auto’ ‘True’, ‘Magnetic’, ‘Grid’ or ‘User’. ‘Auto’ provides magnetic
north heading references which are automatically determined from your current loca-
tion. ‘True’ provides headings based upon a true north reference. ‘Grid’ provides head-
ings based on a grid north reference. ‘User’ allows you to specify the magnetic variation
at your current location, and provides magnetic north heading references based on the
value you entered.
WARNING: If ‘User’ is selected, you must periodically update the magnetic
variation at your present position. Failure to update this setting may result in
substantial differences between the information displayed on your unit and
external references, such as a magnetic compass.
‘ Magnetic Variation’ — displays the magnetic variation at your current location. If ‘User’
is selected for the ‘North Reference’, this fi eld is used to enter the magnetic variance.
Setup Menu — ‘Location’ Tab
Main Menu
Location Tab
190-00294-00_0B.indd 45 9/25/2002, 2:37:30 PM