Detection of unexploded ordnance (UXO) from airborne magnetic data using the Euler deconvolution

Successful applications of the traditional Euler deconvolution depend on accurate assumption of a structural index defining the anomaly attenuation rate of the magnetic sources. An incorrect assumption of the structural index will lead to significant depth error. Recent modification in the technique includes a criterion to determine the structural index of 2D magnetic sources from magnetic profile data. This criterion is based on a correlation between the observed magnetic anomaly and the estimate of an unknown base level using tentative values for the structural index. The tentative value producing minimum correlation is taken as the estimate of the true structural index. In this paper, we extend this criterion to estimate the structural index of environmental magnetic objects from airborne magnetic data. Theoretical examples of magnetic data for a cylinder and a sphere were used to test the criterion. In all cases, the correct index could be estimated by the criterion. The criterion was also tested with airborne magnetic data measured over two case studies of unexploded ordnance (UXO) buried at a test site. It could provide reliable values of the structural index for the two objects, which enabled the Euler deconvolution to locate the objects precisely with an error of depth determination less than 0.1 m from source-to-observation distances of about 3 meters.