Spectral Consistency of Satellite and Airborne Data: Application of an Equivalent Dipole Layer for Combining Satellite and Aeromagnetic Data Sets

We present a novel approach for the combination of aeromagnetic and satellite data applying an equivalent dipole layer and spherical harmonic (SH) expansion of the dipoles. The method involves two steps: (1) inversion for the magnetic parameters of the equivalent dipole layer and (2) conversion of the magnetic parameters into SH coefficients. With this approach, SH analysis can be used for a regional study area, and, for example, the long-wavelength range of aeromagnetic data can be replaced with satellite data. We test our approach on the third, fourth, and fifth editions of the Magnetic Anomaly Map of Australia, which were releveled using independent aeromagnetic data sets for long-wavelength correction. The results indicate that the magnetic compilations leveled to long-haul control lines have a good agreement with the LCS-1 satellite model in the range of SH degree 40 to 110 (corresponding to half-wavelengths between 180 to 500 km), whereas the third edition of the Magnetic Anomaly Map of Australia demonstrates poor control over long- wavelengths in this spectral range. Our analysis suggests that even the carefully processed fifth edition would benefit from the replacement of long-wavelength data with satellite data.