Electromagnetic surveying is carried out to detect the presence of sub-surface variations in the electrical conductivity of the ground. This is useful when attempting to locate buried metallic objects such as pipes, cables and drums. Changing soil properties are also sensed using EM surveying, so features such as mineshafts, localised fill and rapidly changing geology can also be mapped. The method is effective at locating features up to 3m in depth but beyond this the resolution of the technique reduces significantly.
EM methods are quick to acquire, and cover large areas with relative ease. Data processing is very easy, allowing survey maps to be drawn within hours of completing the survey. It is not uncommon for such data to be processed and interpreted on the evening following data acquisition.
