A method for obtaining depth estimates from the geometry of Slingram profiles
An approximate method for deriving conductor depth estimates from the geometry of horizontal coplanar coil Slingram type electromagnetic profiles is based on a transformation of the recorded profile to a form which is free of the influence of coil separation. Depth estimates are derived from an empirically determined linear relationship between the spatial separation of maxima on the transformed profile and the depth of the conductor. Field examples and electromagnetic scale modelling indicate that the method works well on both thin and thick conductors with dips ranging from 90 to 60 degrees. Field examples and model results also show that the method works well when a conductive overburden is present, even if the overburden causes phase inversion. Examples of the application of the method show that while knowledge of the conductance of a target will aid in depth estimation, good depth estimates can be made even if the conductance of the target cannot be determined. Comparative scale model studies of conductors located first in free‐space and then in a conductive host suggest that the method will also give good results for targets located in conductive host rocks.