All surveys are conducted using a "line pattern". In the air, the aircraft fly in straight lines, with the line spacing determined by the client. On the ground, line cutters cut lines through the bush with the line spacing determined by the client. Typically, the spacing of the former is of the order of 100s of metres. The latter, of the order of 10s of metres. What's the difference?

If a conductor is smaller than the spacing and lies between lines, either parallel or perpendicular to them, then it will not necessarily be detected. Airborne should be considered as a "first pass". Follow-up ground surveys will more accurately identify the conductor and its location because of the smaller line spacing. The survey programs are always coordinated by a geo, who, from his/her knowledge of the local geology(helped by the mag maps) can best orient the surveys for maximum detection of conductors.

Down-hole EM surveys are performed to detect "off hole" conductors which might have been missed by ground surveys.

There is science in our, geo's, madness!!!

Respectfully submitted

geoprof