Object Delineation Using Euler’S Momogeneity Equation Location And Depth Determination Of Buried Ferro-Metallic Bodies

The most universal application of magnetic field surveys in environmental studies is the<br>determination of the plan location and depth of buried ferro-metallic objects, such as drums or<br>pipes. Conventional methodology involves presentation of the measured magnetic field as a<br>contour map, manual selection of suspicious magnetic anomalies, and manual or computerassisted<br>interpretation of the plan location and depth estimation of the magnetic sources. The<br>results are dependent on the selection abilities of the interpreter and complicated by the fact<br>that virtually all man-made magnetic objects have significant permanent magnetisation that<br>distorts the observed field.<br>Euler’s homogeneity relationship offers a quasi-automated way to derive plan location and<br>depth estimates of buried ferro-metallic objects from a gridded magnetic data set. Euler’s<br>homogeneity equation relates the magnetic field and its gradient components to the location of<br>the source, with the degree of homogeneity expressed as a structural index. The structural<br>index is a measure of the fall-off rate of the field with distance from the source and provides a<br>way to discriminate between different source shapes. The method is also insensitive to field<br>distortion caused by permanent magnetisation of source objects.<br>This method has been applied to data collected over several test sites, including the Columbia<br>Test Site in Waterloo, Ontario, the US Army Engineer Waterways Experiment Station site in<br>Vicksburg, Mississippi, and EG&G Geometries’ environmental test site at Stanford University,<br>California. The objects buried at these sites are typical of those encountered at sites<br>undergoing environmental assessment (drums, pipes, sheets). The analyses of these data sets<br>have provided characteristic Euler deconvolution signatures and structural indices associated<br>with typical ferro-metallic objects. The solutions obtained indicate the ability to quickly and<br>accurately map the location and depth of buried ferro-metallic objects from gridded magnetic<br>survey data.