An Integrated Approach For Measuring And Processing Geophysical Data For The Detection Of Unexploded Ordnance

Land and water borne electromagnetic and magnetic surveys were performed near<br>the old Lake Erie Ordnance depot in Ohio. The purpose of the study was to<br>determine the presence and subsurface density of unexploded ordnance (UXO).<br>Measurements were carried out within selected onshore and offshore areas using<br>instruments adapted for underwater investigations. A test site with known buried<br>ordnance was prepared in order to establish a base reference for conducting<br>detailed land surveys and transects for the underwater investigation.<br>The interpretation of magnetic field data for man-made metallic ordnance is often<br>difficult because of distortions to the observed field caused by permanent<br>magnetization. The interpretation of the electromagnetic data is dependent on the<br>condition of the metallic content of the object which will have an effect on the<br>electromagnetic field. Advanced data processing and presentation software<br>techniques were employed to determine the criteria for the plan and depth locations<br>of the buried ordnance.<br>The goal of the tests is to help to establish a baseline against which to evaluate<br>future changes in the rate of on-shore deposition of new ordnance. As the magnetic<br>results were limited for the Lake Erie site (low sampling density), magnetic data<br>from a Naval Research Laboratory (NRL) demonstration site at Fort Devens, MA<br>was utilized as a further example for this paper. The purpose was to examine the<br>relationship of higher sampling densities to the accuracy of the plan location and<br>depth calculations of magnetic data.