oa The Impact of AEM Receiver Noise Levels on Detection, Discrimination and Resolvability of Conductive Targets

Lowering receiver noise levels of EM systems has the same benefits as increasing the transmitter signal, because detectability, discrimination and resolvability of target responses improves as the signal to noise ratio increases. Unfortunately the peak dipole moment (where peak dipole moment is considered to be the product of the peak current and the effective transmitter loop area) of TEM systems is often still perceived as being the most significant factor contributing to the signal to noise ratio. The importance of also taking into account the excitation waveform pulse width and shape when determining target response is well published. However, the quantitative effects of reducing receiver noise levels have not received much coverage in literature. Modeling experiments using real VTEM system noise samples from 2006 and 2009 indicates that a four times reduction in system noise amplitude can improve detectability of targets up to 100 m deeper and also enables target conductance and geometry to be modeled as accurately for targets up to 150 m deeper. These improvements are better than can be modeled with a simulated increase in peak dipole moment giving the same signal to noise ratio. This is most likely due to the fact that the real character of noise should be taken into account and not only the standard deviation.