Errors in the Location of a Buried Electromagnetic Source Resulting from Lateral Changes in Ground Conductivity

Measurements of surface magnetic fields may be used to locate a sub-surface oscillating magnetic dipole. However, lateral changes in ground electrical conductivity can affect the location accuracy. Use is made of finite difference solutions to assess the location error. Results show that for reasonable lateral changes in conductivity serious errors can result. Locations based on magnetic tilt angle measurements are more accurate than locations found from the null of the horizontal component.