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RC3000 Antenna Controller Chapter 2 Installation
54
2.4 Final Calibration
The final calibration steps tune up the system for performing automatic location of satellites.
2.4.1 Compass Calibration
Ferrous metal on the vehicle distorts the earth's magnetic field in the vicinity of the vehicle. The flux gate
indicates the direction of the distorted magnetic field. The flux gate calibration procedure provides a
method to correct for this distortion (caused by the vehicle/platform) of the earth's magnetic field and
obtain the vehicle's actual magnetic heading.
Review the discussion of system accuracy in Chapter 1. Since the flux gate calibration only corrects for
distortion of the magnetic field caused by the vehicle itself, it is important that the calibration take place in
an area where the earth's magnetic field is not disturbed by structures or objects containing ferrous
metals. Below is a listing of the characteristics of a good calibration site.
1. Level ground, preferably higher than the surrounding area. Avoid low valleys.
2. Free from structures containing a large amount of ferrous metal. It is of key importance to avoid areas
adjacent to multi-story buildings, railroad tracks, bridges, truck yards, parking lots full of cars, and high
voltage power lines.
3. Trees and wooden objects pose no problem for calibration.
4. Asphalt parking lots can provide a good calibration site. Care should be taken, though, in that asphalt
is often laid over concrete which may contain reinforcing rod.
If a particular location is questionable, walking around with a simple wet compass will often show whether
magnetic irregularities are present. A good site is important since the overall performance of the Satellite
Locator is only as good as its calibration.
Section 3.3.2.9 describes how to perform the compass calibration procedure.