Specifications

University of Pretoria etd – Combrinck, M (2006)
5.3 Airborne survey
5.3.1 Data acquisition and system parameters
The airborne data were acquired with the VTEM system. The VTEM is a helicopter-
borne TDEM system with central loop configuration developed by Geotech. One line is
used to demonstrate the use of the S-layer transform. The data are presented here
courtesy of BHP Billiton. Survey parameters are:
Transmitter Base Frequency Repetition Rate: 25
Transmitter Loop Diameter: 26m
Number of Turns: 4
Peak Current:: 170 A
Tx Dipole Moment: 361,000 NIA
Transmitter Wave Form: Trapezoid (with 40% duty cycle)
Receiver Loop Diameter: 1.1m
Rx Number of Turns: 60
Rx Time Gates: 27 ranging from 0.13ms to 8.9ms
Electromagnetic Receiver & serial number: Geotech VTEM 5
Electromagnetic Transmitter & serial number: Geotech VTEM 5
Length of cable for towed EM bird: 52
Height above ground for EM sensor: 80
The data is shown in Figure 5-19.
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