Soft Locate

Soft locating, also called designating, uses electronic instruments to detect the presence and approximate position of underground utilities from the surface. The most common soft locate methods are electromagnetic (EM) pipe and cable locators, which detect the electromagnetic field surrounding metallic utilities and tracer wires, and ground-penetrating radar (GPR), which uses radar pulses to image subsurface features.

Electromagnetic locators work in two modes: passive mode detects naturally occurring signals on energized cables and radio frequencies re-radiated by metallic objects, while active mode applies a specific signal to a utility (via direct connection, inductive coupling, or a sonde) and then traces that signal along its path. Active mode is more accurate but requires access to the utility for signal application.

Soft locates provide approximate position data that is used to guide the subsequent hard locate (physical exposure) phase. The accuracy of soft locates depends on the method used, soil conditions, utility material, depth, and congestion of the utility corridor. In complex urban environments with multiple utilities in close proximity, soft locate data alone may not be sufficient to differentiate individual utilities, making hard locates essential.