Less Electrodes For Improved Resistivity Profiling

While most resistivity surveys are performed with four moving electrode arrays, one<br>should consider two moving electrode arrays as a way to improve resistivity profiling.<br>Two moving electrode arrays provide gains in survey efficiency and in ease of<br>interpretation. They are particularly well adapted to small scale surveys and to<br>reconnaissance work. They do offer better depth of penetration, for a given array size,<br>than 4 electrode arrays. On the other hand, two electrode array suffer from some loss of<br>depth resolution but this is not that important when one is trying to detect the lateral<br>position of anomalies.<br>The lateral pole-pole array, in which the two electrodes are moving on two parallel lines<br>instead of in line can be considered, for all practical purposes, as a single electrode array.<br>Its response curve over a limited target is a single bell shaped curve that can be<br>interpreted reasonably well with the simple techniques used in potential methods. Depth<br>to target can be evaluated from a single array spacing, eliminating the need to take<br>measurements at multiple spacings. This alone can reduce the total survey time by a<br>factor of 5 or 6.