Methods used to locate underground infrastructure

There are several types of tools that are used to locate utilities such as frequency locators, electromagnetic conductivity, manhole locators, GPR underground detection, etc. More details can be found in the following paragraphs.

What is GPR?

GPR or ground penetrating radar is used in several areas to observe artificial and natural elements located underground. The GPR allows underground infrastructures detection such as tanks detection, metal and non-metallic pipes, electrical lines, conduits like water pipes detection, rebar and post-tension cables inside concrete.

GPR waves are equal to those of a cellular phone or Wi-Fi network, while x-rays require 50 feet of clearance before being used for safety reasons. In general, GPR is the most cost-effective option and the fastest method to test concrete.

The principles of using radio waves to determine the internal structures of soil have long been known. Early work in this area included the use of radio echo sounders to determine the thickness of ice sheets in the Antarctic and Arctic and to measure the thickness of glaciers, which was undoubtedly the greatest success. GPR detection in non-glacial locations was initiated in the early 1970s, and early achievements focused on work done on permafrost soils.

Methods used for Detection of Underground Structures

Electromagnetic Conductivity: This underground duct detection method can be used to calculate ground conductivity and to detect underground tanks or buried metal infrastructures such as electrical duct spindles and concrete pipes.

Cable Locators: These locators are intended to locate electrical and telephone cables. These tools use high or low frequencies to detect buried lines over very long distances.

Manhole Locators: For locating metal utility covers, these manhole locators can be used. These tools can also detect stares that often hide in the ground.

GPR: GPR is a tool that uses multiple frequencies to retrieve data over multiple depth levels. However, the primary detection frequency for underground conduit is 400 MHz. GPR is also used to identify the depth and size of utilities as it is a very effective tool in sandy soils, but not suitable for clay soils.

Suction or Hydro-Excavation: The technique of suction excavation remains a fast and non-destructive method to find and reveal underground infrastructures. This method uses high-pressure air to break the soil, which is then sucked in. This method is also called “soft digging” or “caving”.

Frequency Locators: These locators play an essential role in locating utilities or detecting underground tanks. They can be used to identify the energy emitted by telephone cables, electrical wires and fiber optics buried in the ground. In general, to increase the signal received by the frequency locator, technicians attach a high-frequency transmitter, such as a power tool.

Magnetometers: Magnetometers are tools capable of locating ferrous metal utilities or iron elements buried in the ground. In addition, they have the ability to locate deep infrastructures and the sensitivity of these magnetometers is generally very high.

Advantages of Ground-Based Radar Detection

Increase the Safety of the Work Site

GPR underground detection can be used to locate sewer lines, water, steam, thunderstorms, oil, gas and electrical cables. When GPR detection is used underground, it can help workers and utilities avoid accidental collisions. Therefore, GPR underground detection helps to ensure safety at a job site.

GPR Underground Detection is Accurate

GPR provides accurate images and with the ability to analyze slices at different depths, it provides insight into the depth and orientation of buried objects. Dual-technology systems, which combine ground-penetrating radar and electrical cable detection systems, go further and indicate which ducts contain hazardous power lines.

Challenging Sites

GPR sensors are small and can be used in tight spaces and in any orientation on floors, walls and ceilings. The GPR is applied from the exposed surface and is able to find features in slabs on the ground; it can even identify voids in surrounding materials. Large areas can be mapped effectively by deploying the GPR sensor on a trolley or platform towed by a vehicle.

GPR underground infrastructures detection is effective

While the need for these services is increasing, the funds available to pay for them are difficult to find. Having the ability and reputation to do a thorough job without repeated visits or mistakes is a real competitive advantage. Speed is good, efficiency is better. A professional-quality GPR can provide that benefit. Suppliers must tailor their efforts to site conditions, performing reconnaissance scans to decide where and if a more comprehensive scan is required.


It is always preferable to carry out an evaluation and test without resorting to costly and harmful destructive tests. Even when destructive testing or costly coring is required, targeting them where they are most effective saves time and money.