A new high-sensitivity subsurface electromagnetic sensing system: Part II - Measurement results

In a previous paper, we discussed the design of a new electromagnetic measurement system that employed an Alternating Target Antenna Coupling (ATAC) method to greatly improve the sensitivity and stability of the measurement system. In this paper, we demonstrate this new measurement system by applying it to the detection of various targets, including unexploded ordnance (UXO). First we demonstrate that this new measurement method increases survey efficiency because a richer data set is acquired at each measurement location. Our measurement results show that our current system will detect a standard pipe target at a 2.0-m depth below the earth's surface, which is 0.5-m deeper than the 1.5-m detection depth achieved by current state-of-the-art systems. When the full potential of the ATAC system is realized, we estimate that the projected depth of detection may increase to as much as 9 m. We also show that the measured responses of UXO are different based on the UXO's shape and material composition. The measurement results obtained with our current prototype show that the maximum range for detection of an 81-mm mortar and an 84-mm cannon projectile MK31 to be up to 1.25 m. When the full potential of the ATAC system is realized, we estimate that the projected depth of detection for these targets may increase to as much as 5 m.