Inversion of airborne transient electromagnetic data based on reference point lateral constraint

The airborne transient electromagnetic method (ATEM) has become a popular tool in mineral and resource exploration due to its speed and high efficiency. The distance between two adjacent measured points is minuscule for a flight line because of the oversampling in the ATEM, which results in a sharp change in the horizontal direction. The conventional lateral constraint inversion method accumulates errors and has a significant calculation cost. Therefore, a laterally constrained, segmented inversion method based on a reference point is proposed to reduce errors and improve accuracy. Electrical information about the known logging data is employed as the lateral constraint of the reference point; alternatively, the inversion results of previous point can be used as lateral constraints, which guarantees a continuous inversion profile. The golden-section method is applied to solve the Lagrange multiplier to ensure a quick and effective convergence of inversions. Constraint inversions of a one-dimensional model show that the strategy converges quickly, and the inversion results are closer to the true resistivity of the model. Constraint inversion of a 2D model indicates that lateral constraints considerably reduce the discontinuity of a single-point inversion and smooths the inversion's resistivity pseudosection. Finally, the effectiveness of the proposed algorithm is verified by the inversion of the airborne transient electromagnetic survey data in Xinjiang province.