How Utility Locating Works
The Technology Behind Finding What's Buried
Every time someone digs without knowing what’s underground, they’re gambling. Burst water lines, severed electrical cables, and punctured gas lines happen every day — and most of them are preventable. Professional utility locating exists to take that risk off the table.
Jay uses two industry-standard technologies to find buried utilities — often together on the same job. Here’s how they work.
Electromagnetic Locating (EM)
Electromagnetic locating is the older of the two technologies and the workhorse of the industry. It works by inducing or injecting an electromagnetic signal directly onto a buried pipe or cable, then using a receiver above ground to follow that signal along its path.
EM equipment comes in single and multi-frequency configurations. Single-frequency units are designed for specific utility types. Multi-frequency units offer more flexibility and a better chance of finding everything conductive in a given area.
What EM locating finds well:
- Electrical wires and cables
- Natural gas and propane lines
- Telephone and communication lines
- Any buried utility that conducts an electrical signal
The limitation: EM locating only works on conductive materials. If a pipe is made of plastic, clay, concrete, or asbestos — materials that won’t carry an electrical signal — electromagnetic equipment simply can’t find it. That’s where GPR comes in.
Ground Penetrating Radar (GPR)
GPR works on a completely different principle. Instead of putting a signal on a buried conductor, it fires a high-frequency pulse directly into the ground and reads what bounces back. The time difference between outgoing and returning pulses tells the equipment what’s down there and how deep it is.
GPR is the tool of choice for non-conductive utilities — plastic water lines, concrete structures, septic tanks, and other buried infrastructure that EM equipment can’t detect.
What GPR finds well:
- Plastic water and sewer lines
- Septic tanks and drain fields
- Concrete pipes and structures
- Cast iron lines and other poorly conductive materials
- Any buried object with a different density than surrounding soil
The limitation: Soil conditions have a major effect on GPR performance. Dry sandy soil is ideal — GPR can see deeply and clearly. Wet, heavy clay or very rocky soil reduces visibility significantly. Surface obstacles like trees, stone paths, and ornamental features can also limit where the equipment can be used.
Why Jay Uses Both
EM and GPR each have strengths the other doesn’t. Most real-world job sites have a mix of conductive and non-conductive utilities, which means relying on one technology alone leaves gaps.
Jay carries both types of equipment to every job. The combination gives the best possible picture of what’s underground — and in situations where one tool struggles, the other often fills in the blanks.
Neither technology can guarantee 100% accuracy in every situation. Soil conditions, utility age, depth, and site complexity all play a role. But the combination of EM and GPR, in the hands of someone with 33 years of field experience, gives you the best odds of knowing what’s there before the first shovel hits the ground.
Serving Central North Carolina
Piedmont Locating Services brings professional EM and GPR equipment to job sites across the region including:
Ramseur · Asheboro · Greensboro · Siler City · Archdale · Trinity · Randleman · Liberty · Franklinville · Sophia · Seagrove · Burlington · Mebane
For more information or to request a quote please fill out the form below.