Geophysical Techniques: 3D-IP Method:

Three dimensional IP surveys are designed to take advantage of the interpretational functionality offered by 3-D inversion techniques. Unlike conventional IP, the electrode arrays are no longer restricted to in-line geometry. Typically, current electrodes and receiver electrodes are located on adjacent lines. Under these conditions, multiple current locations can be applied to a single receiver electrode array and data acquisition rates can be significantly improved over conventional surveys.

In a common 3D-IP configuration, a receiver array is established, end-to-end along a survey line while current electrodes are located on two adjacent lines. The survey typically starts at one end of the line and proceeds to the other end. A typical 12 dipole array normally consists of one 300m dipole, followed by one 200m dipole and then nine 100m dipoles, and a 200m dipole at the end of the array. In some areas these spacings are modified to compensate for local conditions such as inaccessible sites, streams, and overall conductivity of ground. Current electrodes are advanced along the adjacent lines, starting at approximately 1000m from the center of the array and advancing approximately 1000m through the array at 100m increments. At this point, the receiver array is advanced 600m and the process is repeated down the line. Receiver arrays are typically established on every second line (400m apart) thereby providing subsurface coverage at 200m increments.