On the estimation of target depth using the single transmit multiple receive metal detector array

This paper investigates the use of the Single Transmit Multiple Receive (STMR) metal detector (MD) array to estimate the depth of metal targets, such as 155mm shells. The depth estimation problem using MD has been investigated by a number of researchers and the processing was performed along the down-track. The proposed method takes a different approach by exploring the MD responses in cross-track to achieve the depth estimation. It is found that the normalized energy spread of the MD output is narrower for shallow targets and wider for deeper targets. Based on this observation, a method is derived to estimate the depth of a target. Experimental results from the data collected at an U.S. Army test site validate the performance of the proposed depth estimator.