You may be on to something but the earth’s signatures need to be mapped by satellite that has the instrumental sensitivity, I doubt that tech exists yet.
It would be a great forensic tool.
Low flying drone with magnetic tape recorder running...picks up ground magnetism (?)with gps location on board drone? Correlate gps with gravity field measurements.
However....someone with a few magnitudes of knowledge greater than me might be able to figure out how to do it.
That newtech oldstyle robber baron org..i.e. Google...maps out street and da’ woild....so maybe task is not that great...