PNI SeaTRAX - Manual (Page 24)

PNI Sensor Corporation DOC#1018154 r02
SeaTRAX User Manual Page 19
points, although it generally is more difficult to obtain a good calibration with just 12
sample points. Also, the maximum number of calibration points is 18.
Note: While the SeaTRAX is shown removed from the host system, the Accelerometer
Calibration may be performed with the SeaTRAX mounted in the host system.
Figure 5-2: Accelerometer Calibration Starting Orientations
5.2.2 Mag-and-Accel Calibration
The SeaTRAX allows for a simultaneous magnetometer and accelerometer calibration.
This requires a good calibration pattern, stable measurements (not handheld), and
installation in the user’s system such that the appropriate local magnetic environment is
present. PNI recommends 18 to 32 calibration points for a Mag-and-Accel Calibration.
The Accelerometer-Only Calibration pattern discussed in Section 5.2.1 will work for a
Mag-and-Accel Calibration. Optimal performance is obtained when all rotations of the
cube are performed towards magnetic north to achieve the widest possible magnetic field
distribution.
Note that combining calibrations only makes sense if all the host system’s magnetic
distortions (steel structures or batteries, for instance) are present and fixed relative to the
module when calibrating. If the Accelerometer-Only Calibration is performed, the user’s
system distortions are not relevant, which allows the SeaTRAX to be removed from the
host system in order to perform the Accelerometer-Only Calibration.