Airmar GH2183, GPS & Heading Sensor - Manual (Page 14)

14
Calibrating the Compass
WARNING: The internal compass may need to be calibrated after the sensor is
installed for maximum accuracy. Perform the pretest below to determine if
calibration is necessary.
CAUTION: Boat—The Pretest and AutoCalibration Procedure must be done in
calm seas in a 0.8 km (0.5 mile) open area away from other boats and ferrous
objects such as structures and aids to navigation. Avoid congested areas and
waters with strong currents as calibration will be difficult and possibly hazardous.
Pretest
Go to an appropriate site.
• Vehicle—Drive to an open parking lot or field, away from other vehicles and
ferrous objects.
• Boat—In calm seas, navigate to an open area of water, 0.8 km (0.5 mile) of
open space away from other boats and ferrous objects.
While making a full circle, compare the heading data to another compass. Check
all headings. If the data agrees, there is no magnetic influence on the sensor. The
compass does NOT need to be calibrated.
If the data does not agree, continue with the calibration instructions below.
How to Calibrate
Calibration can be done in one of two ways.
• Calibrate the compass using the WeatherCaster™ software and a PC.
• Follow the AutoCalibration Procedure below.
AutoCalibration Procedure
IMPORTANT: Calibration requires the vehicle/boat to complete 2 to 3 circles.
IMPORTANT: In the event of a calibration failure, repeat the procedure.
1. At the site where the pretest was performed, select the display page on the
NMEA Instrument that shows Heading.
2. Shut OFF and then turn ON the DC power that is connected to the sensor.
3. Within 2 minutes of cycling power to the sensor, start the vehicle/boat in a slow
[4.5 to 7 MPH (4 to 6 knots)] circular turn that takes about 2 to 3 minutes to
complete.*
If the vehicle/boat completes 1.5 circles within 3 to 4.5 minutes, AutoCalibration
will begin. Heading will stop being reported on any NMEA 0183 or NMEA 2000
display until the calibration is finished.
4. Keep turning in the same circle for 1 to 2 more complete circles.
Do not change the speed or rate of turn through the circle.
5. When calibration is completed successfully, Heading will return to the display.
If calibration fails, the display will flash Heading ON and OFF in 10 second
intervals for 60 seconds. (Display times may vary by manufacturer.)
* The optimum rate of turn is 180 °/ minute: 3°/second, 30°/10 seconds, 45°/15 seconds,
and 90°/30 seconds.