The in-field calibration of a digital compass in the application of end use cannot be taken for granted. Inertial systems (i.e. digital compasses) do not re-calibrate on their own if their magnetic environment changes. The magnetic environment is unpredictable and depends on many factors. If the inertial system is not calibrated to its magnetic environment, its performance could be compromised.
A proper in-field calibration involves orientating the system in various positions over 360 degrees of heading, taking magnetic field measurements at, typically, 12 positions. The inertial system will calculate and save the compensation coefficients and will correct for changes in the application’s magnetic distortions.
Therefore, to optimize performance, an initial system must be calibrated when the system is used at a new location. Ideal in-field environments are not always available. Accordingly, some inertial systems have been developed with advanced adaptive compensation procedures.
Even with adaptive calibration, it is recommended that inertial systems be re-calibrated if the following occur:
- Device relocation
- Changes to user equipment or position of equipment relative to the device
- A large change in operational temperature
- Battery pack replacements
- The addition or removal of ancillary equipment on or near the device