Datum Reduction for Correction of Multi‐Station Geomagnetic Diurnal Variations Using the Least Squares Fitting Method

Abstract

AbstractThe geomagnetic diurnal variation (GDV) is the main influence in marine magnetic survey, especially in offshore and large areas. The multi‐station method is the main technique to deal with the GDV correction. However, to diminish the difference between the magnetic field data and multiple stations data, the correction datum of the secondary stations must be reduced to the main station.In marine sounding the least squares fitting (LSF) method has been applied in the interpolation of the height of the tide. Considering the similarity of the influence mechanism of the tidal variation and GDV, the LSF method has been introduced in the datum reduction. The datum of the secondary station can be corrected, which is decided by the expansion and contraction of the amplitude, the translation of the time (phase) of the diurnal variation of the main station, and the residual error of the diurnal variation correction of the main and secondary station is minimum with the LSF method. The validity of the method has been testified by the observed synchronous data of the multiple stations.The results show that the LSF method can be applied when the characteristics of the diurnal geomagnetic variations of the stations are similar, which requires a short synchronous observation period. Otherwise the synchronous correction (SC) method should be qualified.It is concluded that the LSF method can be effectively applied to the datum reduction with multi‐station GDV correction, therefore the difference of the magnetic field which is caused by the datum can be diminished and the correction precision can be improved in magnetic survey of offshore and large areas. Moreover the reduction method must be adjusted to the need of the practice. In addition, the LSF method can be applied to the determination of the time difference and the correction value interpolation.