Garmin GPS III Plus - Manual (Page 92)

Position Settings
Position Format is used to change the coordinate system in which a given position
reading is displayed. The default format is latitude and longitude in degrees and minutes
(hddd°mm.mmm’). The following additional formats are available:
• hddd.ddddd° — latitude/longitude in decimal degrees only
• hddd°mm’ss.s” — latitude/longitude in degrees, minutes, seconds
• UTM/UPS — Universal Transverse Mercator / Universal Polar Stereographic grids
• MGRS — Military Grid Reference System
• British Grid • German Grid • Irish Grid
• Maidenhead • New Zealand • Swedish Grid
• Swiss Grid • Taiwan Grid • User UTM Grid
• Loran TD (See following page.)
Map Datum allows you to select the datum reference used to determine where a given
position is. The default setting is ‘WGS 84’. Although over 100 datums are available (as
listed on page 92-94), you should only change the datum if you are using a map or
chart that specifies a different datum.
Make sure the settings under the ‘Position’ tab
of the III+ match that of the map or chart. This information should be displayed
somewhere on the map or chart. If the information is not present, contact the map
or chart maker to determine what position format, datum, heading and units of
measure are being used for the map or chart.
WARNING: Selecting the wrong map datum can result in substantial position errors.
When in doubt, seek assistance or use the default WGS 84 datum for best overall
performance.
To change the position format and/or map datum:
1. Highlight the ‘Position Format’ or ‘Map Datum’ field and press ENTER.
2. Select the desired setting (using the rocker keypad) and press ENTER.
Only the latitude/longitude,
UTM/UPS and Maidenhead
settings apply worldwide. The
additional grid settings are
only valid for a specific region.
Datums are used to describe
geographic positions for survey-
ing, mapping, and navigation
and are not actual maps built
in the unit. Use WGS 84 unless
your chart specifies otherwise.
82
REFERENCE
Setup Menu: Position