GPR in Montreal – How does GPR work?

Ground-penetrating radar is used in many industries and is particularly useful in the fields of engineering, mining, archaeology, and road maintenance. This equipment is used to determine the characteristics of underground utilities such as gas lines, water lines, sewers, culverts, etc. The data obtained by GPR methods allows contractors to plan trenchless construction activities with minimal damage to existing underground utilities.

GPR Montreal – What is GPR?

Ground-penetrating radar (GPR) is used in many areas to observe man-made and natural features. Ground penetrating radar allows for the detection of underground tanks, metallic and non-metallic pipes, power lines, GPR detection of underground conduits such as water pipes, reinforcing bars and post-tensioning cables inside concrete.

Ground-penetrating radar waves are equal to those of a cell phone or Wi-Fi network, while x-rays require a 50-foot clearance before being used for safety reasons. In general, ground-penetrating radar is the most cost-effective option and the fastest method of testing concrete.

The principle of using radio waves to determine internal ground structures has been known for a long time. Among the earliest works in this field, the use of radio echo sounders to determine the thickness of ice sheets in Antarctica and the Arctic and to measure the thickness of glaciers is undoubtedly the most successful. Ground-penetrating radar sensing in non-glacial areas was initiated in the early 1970s. The first achievements focused on work on permafrost soils.

Depth and frequency of GPE detection

Ground-penetrating radar generally uses signals in the microwave band. For applications requiring greater accuracy, such as locating pipes in concrete, it uses higher frequencies. These frequencies do not penetrate as deeply, but they offer much better resolution. However, for applications requiring much greater depth, it uses frequencies between 12 and 500 MHz.

Depending on the subsurface material, these frequencies can penetrate thousands of feet deep. The deep application is particularly useful for surveying areas where the contents of the ground are unknown. Ground-penetrating radar is equipped and designed for only one type of application, an important aspect to consider when searching for solutions.

However, some products emit multiple frequencies simultaneously, such as the Quantum Imager triple frequency GPR system. These solutions offer a unique approach and implementation that combines frequencies to provide an unprecedented level of depth and accuracy.

Uses of utility mapping

Underground utility mapping takes advantage of GPR technology to increase the accuracy of its work when combined with traditional location methods. Ground-penetrating radar can be used to discover unmarked utilities and structures, map the subsurface, and conduct excavation projects. For these types of applications, the benefits are significant.

Antenna type

There are several types of antennas for this radar. The air-coupled horn antennas are suspended several tens of centimeters above the ground. Ground-coupled antennas are towed on the surface and core antennas, which can be inserted into the ground after drilling. These antennas are not suitable for road structures. The majority of ground-penetrating radar systems operate in the time dimension, sending out very short electromagnetic signals and recording the returned message as a function of time.

Is GPR difficult to use?

Ground Penetrating Radar is not only a non-intrusive and effective detection method, but it is also easy to use. It sends out signals that are returned when they come in contact with an object buried in the ground. A ground-penetrating radar specialist can measure the depth of the ground based on the time it takes for the electromagnetic waves to bounce back. The operation of this machine is simple, but it takes years of experience to correctly interpret the data generated. For this reason, a layman cannot use the machine himself; it takes an expert to operate it.

Is GPR scanning effective?

GPR is a very effective tool for locating public services. It is possible to locate utilities, but it is difficult to identify their types. A significant marker, such as a valve or meter, can be tracked to identify the type of facility.

In addition, the surveyor can locate PVC pipes and other non-conductive utilities, even though these objects emit a weaker signal than conductive elements. However, specialists in the use of the Ground Penetrating Radar are able to accurately interpret the information produced.

Ground-penetrating radar can also be used to cross-check the measured location and depth of buried utilities against known measurements to verify the accuracy of plans.

Conclusion

It is important to master the use of GPR in order to carry out your own measurement campaigns. To do this, you must carefully choose the type of GPR, including the central frequency or frequency range. This allows you to take full advantage of the quality of the measurements obtained. Furthermore, the selection of the measurement criteria, as well as the processing and interpretation of the data, requires certain knowledge on the part of the user. Do not hesitate to contact us for more information on GPR surveying!