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GPSMAP 495 Owner’s Manual
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.
