Measuring the orthogonality error of coil systems

Recently, a simple method was proposed for the determination of pitch angle between two coil axes by means of a total
field magnetometer. The method is applicable when the homogeneous volume in the centre of the coil system is large
enough to accommodate the total field sensor. Orthogonality of calibration coil systems used for calibrating vector
magnetometers can be attained by this procedure. In addition, the method can be easily automated and applied to the
calibration of delta inclination–delta declination (dIdD) magnetometers. The method was tested by several independent
research groups, having a variety of test equipment, and located at differing geomagnetic observatories, including:
Nurmijärvi, Finland; Hermanus, South Africa; Ottawa, Canada; Tihany, Hungary. This paper summarizes the test
results, and discusses the advantages and limitations of the method.