Two-dimensional position measurement using magnetoquasistatic fields

Two-dimensional (2-D) measurements of the magnetoquasistatic fields generated from a magnetic dipole (an electrically small current loop) located above the earth are compared to calculations using complex image theory. The magnetoquasistatic coupling between a vertical (i.e., surface normal parallel to the earth) emitting loop and seven vertical receiving loops was measured in a two-dimensional x−y grid of 27.43 m by 27.43 m, all above the earth, where the receiving loops were located outside this grid. Inverting the theoretical expressions to estimate two-dimensional position from measured field values resulted in an average geometric position error of 1.08 m (100th percentile of the measured grid), and an average error of 0.89 m for 95th percentile of measured grid.