Reply by the author to R. Ignetik

The failure of Ignetik to recognize the logic underlying my approach to polygonal‐loop modeling demonstrates a need to present some points more clearly. The starting point was that I wanted to represent the transmitter as an array of vertical magnetic dipoles rather than horizontal linear dipoles. The reason for this was to minimize the computation needed for downhole receivers and multiple transmitter loops. The layered‐earth Green’s tensor elements for horizontal linear dipoles for a general “receiver” point are very complicated for the N‐layer case. Those for the vertical dipole are very simple and require much less computation.