Depth of Cover

The vertical distance from the ground surface to the top of a buried utility. Depth estimated by an electromagnetic locator or read off a radar record is an interpretation; depth measured at an open test hole is a measurement.

Depth is the weakest number on most locates and the one most often misread as precise. An electromagnetic locator infers depth from the shape of the field around the line, so anything that distorts that field — a parallel line, bonded grounding, bleedover onto adjacent metal — moves the reading. Radar returns a two-way travel time that must be converted using an assumed soil velocity, which varies with moisture. Where a design or a bore path depends on the number, the answer is a test hole.