LETTERS TO THE EDITOR (January 13, 1992)

In reference to the article “Air prospecting less in demand” (T.N.M., Dec. 2/91), it is true there is less flown now than in the past. But what people must realize is that now the quality of the collected data, the range of processing possibilities and the myriad of objectives to which it can be applied beyond base metal exploration (yes, even to gold) indicate that airborne magnetic and electromagnetic (EM) surveying should not be asked to exit stage left.

With respect to EM’s heretofore historical role as a massive sulphide detector, fixed-wing time-domain EM systems have a depth penetration greatly in excess of 150 ft. (a figure stated in the article). Switch feet to metres and multiply by three, or even four, to arrive at the more correct number. Rolf Pedersen

Senior Geophysicist

Geoterrex Ltd.

Ottawa