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Navigation Setup: Map Datums (continued)
To define a user datum:
1. Highlight the ‘MAP DATUM’ field, and press
E
.
2. Scroll through the map datum options until ‘User’
appears, and press
E
.
3. Enter the five parameters of the map datum—‘DX’,
‘DY’, ‘DZ’, ‘DA’, and ‘DF’—using the rocker keypad,
and press
E
.
The signs of each value should fol-
low the convention: WGS 84 +/- local geodetic system.
4. Highlight ‘SAVE?’, and press
E
.
Navigation Setup: CDIScale
The course deviation indicator (CDI) field lets you
select the range of the CDI bar scale on the Highway
Page. Four scales are available: +/- 0.02, 0.25 (default),
1.25, and 5.0 miles or kilometers. Note: This CDI
value represents the full scale limits (left or right from
center) of the CDI.
To enter a CDI scale setting:
1. Highlight the ‘CDI’ field, and press
E
.
2. Select the desired setting, and press
E
.
Navigation Setup: Units of Measure
The GPS 12 lets you select statute (default), nauti-
cal, or metric units of measure for all speed and dis-
tance readouts.
To change the unit of measure:
1. Highlight the ‘UNITS’ field, and press
E
.
2. Select the desired units of measure, and press
E
.
Navigation Setup: Heading Reference
The GPS 12’s heading information can be displayed
referencing magnetic north (automatic or user-defined),
true north, or calculated grid headings. The default set-
ting is automatically-calculated magnetic north, which
is suitable for most applications.
To select a heading reference:
1. Highlight the ‘HEADING’ field, and press
E
.
2. Select the desired heading reference, and press
E
.
To enter a user-defined magnetic heading:
. 1. Select ‘User Mag’ and press
E
.
2. Enter the degrees and direction of magnetic variation,
and press
E
.
45
The user datum feature
allows you to define the
earth model used to calcu-
late position coordinates.
WA R N I N G: Incorre c t
entries may result in sub-
stantial position errors.
REFERENCE
Navigation
Setup
To enter a user- d e f i n e d
magnetic variation, select
the ‘User Mag’ option and
enter the desired direction
and degrees.
GPS12B 1/13/99 4:28 PM Page 45