The term ‘pipe and cable locating’ is a bit of a misconception for starters.

An electromagnetic field (EMF) locator does not locate pipe and cables. It detects an electromagnetic field as it transitions along a metallic pipe or cable. The electromagnetic field is then located by the receiver.

Locators will know that other contractors on site will think that with a wave of an EMF receiver, any assets will be magically located. The reality is, there are limitations for EMF locators, just as there are for ground penetrating radar (GPR) locators.

By now, most people are aware that service locating devices exist, but there is still limited knowledge on construction sites as to what equipment or method is required to locate specific types of pipe material.

EMF is the essential tool in a locator’s truck. It works in a more diverse range of ground conditions; it has the ability to trace target lines and is generally easier and faster to learn the basic principles of use, and when and how it can be used. The drawback is that it relies on the service being metallic, having undamaged metallic trace wires or the service needs to be accessible to insert a traceable rod to locate. It does not locate direct buried optic fibre or non-metallic pipes such as PVC or nylon without having a trace wire.

GPR is used for mapping or locating non-metallic pipes and underground storage tanks. GPR transmits a small electromagnetic wave through an antenna and then a pipe or cable reflects energy back to the ground surface and received by the antenna. The depth and resolution of the target is related to antenna frequency, power transmitter and the dielectric of the ground. In layman’s terms – GPR’s effectiveness is highly reliant on ground conditions due to the electrical conductivity of the ground or water and clay content.

However there still remains a belief that a service locator’s GPR can show a perfect skeleton buried in a grave. The reality is that GPR does not show a perfectly formed pipe on the screen – in a good scan it will show a hyperbola. They cannot tell you the size or material of a pipe or cable or what service is within that pipe. The only thing to do is Hydro Excavate / Pothole to verify and record what you find. Hydro Excavation is the most accurate way for this to be done.