Attitude corrections of attitude rotational invariant in airborne frequency-domain electromagnetic method

There exist attitude errors resulting from the change of coupling between the coils and the earth for attitude angle change in the course of flight measurement of airborne frequency domain electromagnetic instruments. According to differences of sources, the attitude errors can be divided into the direction errors and the position errors. In order to eliminate the effect of attitude errors, this study firstly derives the electromagnetic tensor attitude rotational invariant from the coil configuration of tri-axial transmitter and tri-axis receiver in layered earth model. Then the cosines of roll angle and pitch angle can be deduced on the basis of superposed dipole model, achieving the correction of position errors of invariant. Compared with the traditional attitude correction algorithm, the attitude correction algorithm of invariant does not need to measure any attitude information. From the simulation results, the attitude correction algorithm of invariant can achieve the similar effects of traditional attitude correction algorithm in three common coil configurations. In the common H-type and K-type three-layer earth model, the relative error of invariant after correction is less than 0.1%, which proves the feasibility of the attitude correction algorithm of invariant.