GPR Usage and Affecting Factors
Ground penetrating radar (GPR) is a key tool in detecting the location of underground utilities and other subsurface elements. GPR units contain at least one antenna which is moved over the ground surface being investigated. Several types of units of varying strengths may be used depending on the needs of the project in question. GPRS Project Managers will assess the site and make a determination as to which type of radar is the best fit for the job.
As the antenna(s) are moved over the ground they work to transmit radio waves of a certain frequency into the surface- the ground or slab in question. Once the radio waves hit the surface, they dissipate directly into the ground if there are no elements beneath. If the waves hit a buried subsurface element such as pipe, conduit, or other utilities, this element bounces the wave signal back to the radar’s antenna.
The signal data is recorded and interpreted by an experienced GPRS Project Manager in order to determine the size, depth, and location of various elements. Since different readings tie to different results, it’s up to the expertise of the Project Manager to analyze the outcome.
This info is used to provide you with a clear understanding of what lies beneath the surface.
While GPR is a highly accurate tool, there are a few things our Project Managers take into consideration before assessing a site. A few things which might impact the use of the GPR equipment includes ground conditions, presence of other buried materials (such as roots or stones), and weather conditions. GPRS Project Managers receive extensive training focused on managing these variables in order to produce the best result.
Ground Conditions and GPR Accuracy
Moisture plays a large role in GPR’s ability to produce an accurate reading. Moisture has an impact on the conductivity of radio waves- once the radar waves hit a pocket of saturation, they are bounced back to the antenna. If the radar hits moisture before it reaches a buried object, this will have an impact on the results. Different types of soil hold on to moisture in different ways- clay is wetter and holds on to more water than sandy or rocky soil. Areas with a high water table create moisture issues as well. In addition to water, certain types of soil contain higher levels of minerals or salts which impact conductivity.
For these reasons certain areas may be harder or easier to scan. Our Project Managers may review local soil maps and other information in order to determine which method of utility locating is the best fit for the job.
The flatter and more even the ground, the easier it becomes to maneuver a GPR unit over it. An uneven surface makes it more difficult for the radar to connect with and send a strong signal into the ground, in turn impacting the accuracy of the results.
GPRS Project Managers employ various types of radar devices depending on the needs of the project in question. If a certain radar unit is incapable of scanning to the desired depth, other units can be used until a sufficient reading is produced. The types of equipment used by GPRS have a wide range of detection capable of meeting all utility locating needs.
Can GPR be used in all types of weather?
Since moisture has such an impact on GPR, weather plays a role in achieving accurate readings. Snow and rainfall or flooding create tough situations for the use of GPR. In snowy or wet conditions the use of GPR would not be recommended.
Detecting Non-conductive materials
Pipes made of PVC, plastic, and other non-conductive materials are often used in buried utilities. The pipes themselves do not interact with the radar to create a signal, but the material or void space inside of them can. While it is more difficult to discern a reading on a non-conductive material, it’s a common occurrence which our Project Managers are trained to work with.
Determining if GPR is the Right Tool for your Project
Our Project Managers are subject matter experts in the art of utility locating. Their knowledge of GPR and its limitations is second to none, making GPRS the clear choice in serving your GPR needs. Each project presents its own unique challenges which are assessed on a case-by-case basis in order to determine the best course of action. In the event that conditions are not suitable for GPR scanning, an alternative recommendation can be made by one of our Project Managers. While GPR is not always the best choice for each situation, we are able to recommend various other types of equipment that can be successfully implemented to serve your project’s needs.