UTEM uses a large, fixed, horizontal transmitter loop as its source. loops range in size from 300m x 300m up to as large as 4km x 4km. Smaller loops are generally used over conductive terrain or for shallow sounding work. The larger loops are only used over resistive terrain. The UTEM receiver is typically syncronized with the transmitter at the beginning of a survey day and operates remotely after that point. The clocks employed - one in each of the receiver and transmitter - are sufficiently accurate to maintain synchronisation.
Measurements are routinely taken to a distance of 1.5 to twice the loop dimensions, depending on the local noise levels, and can be continued further. Lines are typically surveyed out from the edge of the loop but may also be read across the loop wire and through the centre of the loop, a configuration used mainly to detect horizontal conductors. The UTEM 3 system, for many years the UTEM workhorse, has been superceded in many applications by UTEM5.
Lamontagne's BHUTEM - the borehole version of UTEM - has surveyed at depths of up to 3000+ metres.
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