Analysis of spheroidal electromagnetic induction response as a model of unexploded ordnance

Identifying, detecting, classifying and separating unexploded ordnance is one of the essential needs of countries and societies that have been involved in war. Marine mines submerged in seawater or buried in land are a common danger in many areas of the world. The majority of mines are composed of metal and explosive materials. There are many non-destructive schemes for detecting the location, orientation and depth of a metallic mine (modeled as a perfectly conducting sphere and spheroid). This methods of exploration of such materials, which are mainly based on geophysical methods, have a special importance and capability in terms of economy and safety. A major challenge when detecting a metallic object is discriminating the object, such as an unexploded ordnance (UXO), from the noisy environment. It takes time and resources to identify the object, especially due to false signals from other metal objects and cultural features such as metal buildings, pipelines, and oil well casings. By measuring the secondary response of an electrically conductive object which is placed in a low frequency primary magnetic field, distinct spectral characteristics such as electrical conductivity, magnetic permeability, object geometry, and size can be obtained. The electromagnetic induction method is an efficient geophysical method that is used to identify land mines and sea mines. This method (EMI) is one of the frequency domain methods that has been used for this purpose. This technique takes into account Eddy-Current response (ECR) induced on the conducting marine mines as well as Current-Channeling response (CCR) associated with the perturbation of currents induced in the conductive marine environment. In general, in the process of processing data obtained from geophysical surveys, and especially in the electromagnetic induction method, such anomalies are modeled with simple geometric objects such as spheres or spheres. In the first step of data interpretation and to determine the dimensions of the model that indicates the type of mine or bomb and also to determine its location, it is necessary for the interpreter to have a clear view of how the electromagnetic induction response depends on the geometric and physical parameters of such materials. For this purpose, in this article, how the changes and behavior of the received electromagnetic induction response in the receiver coil are investigated according to the depth, dimensions and orientation of the abnormality. The graphs obtained are examined and analyzed according to the mentioned variables, and the obtained results, while qualitatively determining the state of abnormality to a large extent, can be calculated in numerical methods. Geometrical and physical quantities of anomalies become useful.