NORTHROP GRUMMAN NAVITWIN IV, Operation, Installation And Service Manual, Page: 76 / 164

056360/E NAVITWIN IV
6-4 Magnetic Compass Heading Calibration
Determining magnetic compass heading correction values
1. Make sure that the magnetic variation is set to 0.0° in the Manual
Settings menu.
2. Make sure that the calibration is disabled (option ’use cal tab’
unchecked) in the User Setup / Magn. Cal. Tab.
3. Select a manual steering mode.
4. Commence a continuous, very slow and steady turn. The vessel
must turn through one full circle (360°) at least.
5. While the vessel is turning, com-
pare the indication at the steer-
ing magnetic compass with the
magnetic compass heading val-
ues shown on the NAVITWIN IV
display.
At every full 10° of the steering
magnetic compass heading (0°,
10°, …, 350°), note the display
value.
6. Enter the observed display val-
ues in the magnetic compass
heading calibration table form
(blank form included in the
appendix of this manual).
7. Calculate the required correc-
tion value for each heading
value and enter it in the calibra-
tion table form.
The correction value is the offset
which must be applied to a
given display value in order to
obtain the steering magnetic
compass heading.
Example:
steering magnetic compass
heading = 0°,
display value = 0.8°,
correction value = –0.8°.
0
Mag. Compass
Heading
Mag. HDG
Display
(uncalibrated)
Correction
Value
10
MAGN
COMP
000.8
0
Mag. Compass
Heading
Mag. Hdg.
Display
(uncalibrated)
Correction
Value
10
0°
Mag. Compass
Heading
Mag. Hdg.
Display
(uncalibrated)
Correction
Value
10°
– mag. hdg. display
= correction value
mag. compass hdg.