oa The pulled array transient electromagnetic method

The mapping of subsurface resistivity structures using transient electromagnetic soundings, TEM, has gained an important role in hydrogeological investigations in Denmark. Regional mapping with TEM have produced resuits, which leaves no doubt as to the ability of the method to delineate freshwater sandy aquifers in well conducting hosts of Tertiary clays. These results have been achieved measuring in a dense grid and do demonstrated the necessity of estimating the data quality and variation by correlating adjecent data sets to reveal distortion and multidimensionality of the measurements. The fact that these investigations are often carried out in densely populated areas, where the cultural noise level is high, accentuates this necessity even more (Christensen and Sorensen, 1994).