What Is Electromagnetic Locating?

What Is Electromagnetic Locating?

Underground utility locators are critical stakeholders in the damage prevention process. They are responsible for identifying and marking the locations of all facilities potentially in conflict with a proposed ground disturbance. There are various ways for a utility locator to accomplish this, including direct connection (conduction) and passive (induction) electromagnetic locating. These are versatile methods of locating buried utilities, but how does this technology work?

Electromagnetic utility locating technology consists of two main parts: a transmitter and a receiver. The transmitter emits a frequency selected by the operator that induces onto nearby pipes and cables. The receiver detects these radio frequencies, and the operator is then able to accurately locate and trace the pipes and cables. 

When locating electromagnetically, conduction locating is the preferred method of locating metallic utility lines. The transmitter is placed next to an access point for the target line being traced (typically a valve, utility box, utility vault, or other point where direct contact with the line can be made). A connection lead from the transmitter is connected to the target line and a second lead is connected to the ground.

Once set up, the transmitter is adjusted for frequency and power output to match the properties of the target line being traced, surrounding soil and other utilities nearby. Applying the correct frequency is essential to prevent electromagnetic coupling or bleed off to other metallic utilities or objects. The receiver is then set to the same frequency as the transmitter, gain control adjusted accordingly, and the signal which is sent from the transmitter through the target line is traced and marked on the surface.

When there is no surface access to the target line, the other electromagnetic locating option is induction locating. Although induction is not as accurate as conduction due to increased electromagnetic coupling or bleed off, it can be effective when used properly. The transmitter is placed on the surface over the point where the target line is thought to run. Once the target line is located, it is traced with the receiver using the same method as direct connection. This method can also be used to perform an inductive search to locate unknown or abandoned lines.

As electromagnetic locating equipment and technology continues to improve every single day, the Training Standards Committee (TSC) works collaboratively to identify important ground disturbance and damage prevention topics like this and implements these important lessons into their training standards. If you have an interest in these types of topics or want to know more about what the TSC does, reach out to TSCAdmin@utilitysafety.ca.

Mark Hemsworth - OH&S Safety Consulting and Training Solutions.