How Does Ground Penetrating Radar (GPR) Work?
Ground-penetrating radar, or GPR, is really a method of surveying subsurface materials. Using electromagnetic radar pulses, GPR can image materials in the ground, concrete, rock, ice and other structures without disturbing the surface. Within the last few decades, the technology has come up to now that it?s now one of the common approaches for surveying subsurface materials.
There are a few reasons for this development. GPR offers many perks over other methods, including cost and accessibility. The largest benefit, however, is its non-destructive approach. By leveraging electromagnetism, ground-penetrating radar systems enable operators to survey a wide variety of subsurface materials and detect a straight wider range of objects within that material without digging a single hole.
But so how exactly does GPR work? How do this cost-effective and highly mobile system help professionals locate telecommunication lines or academics seek out archaeological artifacts, all without breaking the top?
The Science of Ground Penetrating Radar
an archaeologist digging in the ground with a small hand tool
Ground-penetrating radar functions by sending a little pulse of electromagnetic energy in to the ground and measuring changes and contrasts in the signal when it?s reflected in the receiving antenna. When these pulses enter the material, it produces reflections in line with the conduction and dielectric properties of the objects within and also the surrounding material.
It works like this:
A transmitting antenna sends a pulse of electromagnetic energy into the ground.
This pulse passes through the bottom and subsurface objects and is then distorted by dielectric and conductive properties.
The pulse travels back again to the receiving antenna and displays the distortions and contrast between objects in the soil and the soil itself.
By analyzing the signal distortions in the signal reflection and examining the contrast between your surrounding ground and objects, operators can infer what?s in the underlying material. It?s worth noting these methods also detect variations and inconsistencies in the bottom material?s composition, such as voids or loose soil.
These waves can handle traveling through many materials, including various soil substrates, concrete, rock, debris and also water, yet these materials all have different conductive and dielectric properties that impact the reflection of the electromagnetic waves. The strength and amplitude of the reflection are determined by the dielectric and conductive properties of both materials.
For instance, moving from dry sand to wet sand produces an extremely strong reflection and a sharp contrast in measurement. Moving from dry sand to limestone, however, will produce much less contrast because the dielectric is quite similar. It?s also worth mentioning that material with higher dielectric properties slows radar waves and prevents them from penetrating as deeply.
When performing a survey with a GPR system, electromagnetic pulses are fired into the ground rapidly ? this is exactly what?s known as a scan. A GPR scan measures a surface by moving consistently across the surface and firing continuous pulses of energy into the ground to measure and analyze these contrasts and distortions.
Depth and Frequencies
person utilizes depth and frequencies of the Quantum Imaginer Triple Frequency GPR System
Ground-penetrating radar typically uses signals ranging in the microwave band. In applications that want more accuracy, such as for example locating conduits in concrete, it uses frequencies toward the higher end. These frequencies don?t penetrate Additional info , however they provide much better resolution.
Alternatively, for applications that want much greater depth, it uses frequencies in the number of 12 MHz to 500 MHz. Depending on the subsurface material, these frequencies can penetrate thousands of feet deep. Depth application is especially useful in surveying areas where there isn?t much certainty in regards to what?s in the soil.
Many GPR systems come equipped and so are designed for only one type of application, so this is an essential requirement to consider when considering solutions. However, some products emit multiple simultaneous frequencies, such as our very own Quantum Imager Triple Frequency GPR System. These solutions offer a unique approach and implementation that combines frequencies to supply an unprecedented degree of depth and accuracy.
Understanding GPR Systems
people use laptops and tablets at a table for understanding GPR systems
Discussing ground-penetrating radar from these perspectives focuses on the science and technology behind it. And while it seems complicated, using a GPR system and interpreting the info requires just a minimal amount of training and practice. Making the effort to understand how GPR systems work in the real world goes a long way toward becoming proficient with it
Science and technology aside, GPR systems rely on several different tools to accurately survey subsurface materials. A typical system almost always includes the next:
Two antennas: one for transmitting and another for receiving
A computer and display for collecting and analyzing the info
A power supply for powering everything
Once the antennas transmit the electromagnetic waves, the wave distortions are measured and transmitted to the computer and display images and graphs concerning the subsurface material. With this information, the operator can infer the kind of object or objects present as well as their depths.
Each of the calculations necessary to display accurate readings happen behind the scenes, using the software. Measuring depth, for instance, is really a precise calculation determined by the time it requires for a signal to go from the transmitting antenna in to the subsurface and reflecting the receiving antenna.
It?s important to mention that this data isn?t passive or only readable in the field. While instant feedback is obviously an element of GRP, the info collected because of it is sharable and analyzable. With the proper GPR software, operators can collect vast amounts of data about the subsurface they?re surveying and share it with colleagues for further processing. Moreover, GPR systems can be coupled with additional technologies, such as for example GPS or other mapping systems. This may improve large-area scanning and offer a wealth of data to professionals who require it.
As the technology behind GPR is immensely useful, it?s worth taking the time to understand the machine all together. From the computer to the software running on it, every part of the system comes together to get, process, display and share data with operators and professionals in meaningful ways.