Norton, Jeannemarie (Battelle - Oak Ridge Operations) | Beard, Les (Battelle - Oak Ridge Operations) | Gamey, Jeffrey (Battelle - Oak Ridge Operations) | Doll, William (Battelle - Oak Ridge Operations) | Sheehan, Jacob (Battelle - Oak Ridge Operations)
We investigate optimal sensor configurations of total-field magnetic surveys for near-surface applications such as unexploded ordnance detection. Vertical gradient configurations are often used because they effectively remove longer wavelength cultural or geological features and attenuate coherent noise. However, they also result in additional attenuation from the signals of interest. Using survey design techniques we demonstrate that a vertical gradient configuration is inferior to a configuration with all the sensors at the same level and with half the sensor spacing. This result is consistent with potential field theory where knowledge of the field at one elevation can be used to predict the field anywhere above that layer. The coherent noise suppression advantage of the vertical gradient can be achieved using a reference sensor which is ideally placed closer to the dominant noise source. We demonstrate the survey design techniques and results on low-level unexploded ordnance detection from a helicopter.