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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.

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). 

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.

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.