Geologic structure is often revealed by dislocations of magnetic axes and contacts. Points of dislocation can often be traced from one magnetic unit to another to define the axis of associated fault plane. The horizontal fault displacement can also be measured from the magnetic axis offset. Vertical displacements may be revealed by a change in the anomaly flanks; the down-thrown side will have a broader response reflecting greater depth. Vertical displacements can also bring a wider or narrower cross section to basement surface and the fault may be revealed by a sudden change in apparent width.

The ability to recognize these often subtle structural details is limited by the quality of the magnetic map. Accurate flight line positioning is a critical necessity but the quality of the griding and map making process is also of fundamental importance. To illustrate, a model scenario consisting of narrow parallel dykes, with fault off-sets of 25, 50 and 75 metres, was created. The corresponding profile data, at 100, 140 and 200 metre line spacing, was compiled using a conventional minimum curvature method as well as the new GT-GRID technique. At 100 m. line spacing, there is a little chatter in the conventional map but both can marginally resolve even the 25 m. displacement. At 140 m. line spacing the interpolation oscillations in the conventional map have visibly increased and by 200 m. are very pronounced. It can be argued that the fault displacements are still notable along the anomaly ridge, particularly when the model is presented for reference; however, the GT-GRID presentation clearly presents the dislocations not only along the ridge but also along the flanks of the anomalies.