Dictionary:Depth of investigation
1. The depth beyond the surface to which an exploration system can effectively explore. Depends on array design, spacing, property contrast, body geometry, and signal-to-noise ratio. The maximum depth at which interfaces or the sources of anomalies are resolvable considering the signal-to-noise ratio and other measurement considerations. Also see skin depth. 2. The radius of a cylinder about a logging sonde within which 50% of the signal comes for electrical tools, 90% for nuclear tools, a loosely defined standard. See Figure D-8 and Spies (1989).