Alldredge's method of rectangular harmonic analysis has been re-examined. After correction of errors, it is found to give improbable values between the data points and wild values outside them. A much more realistic model has been obtained by (i) determining only the most significant coefficients (those that exceed their standart deviations, obtained by an iterative process), (ii) introducing new parameters to allow for a linear trend across the region and (iii) increasing the scaling factors so that the sinusoids start and finish outside the region. Modification is the most important for improving the interpolative qualities of the model. Modifications (ii) and (iii) reduce, but do not entirely eliminate, the wild values near the edges.
AGU Index Terms: 1545 Spatial variations (all harmonics and anomalies);
Keywords/Free Terms: Geomagnetism, modelling, regional field.
JGR-Solid Earth 96JB01885
Vol. 101
, No. B12
, p. 28,205