Ground Penetrating Radar

concrete scanning

Ground Penetrating Radar Services

service overview

GPR stands for Ground Penetrating Radar. It is a geophysical method that uses radar pulses to image the subsurface. GPR is commonly used for non-destructive testing and subsurface imaging in various applications, including construction, archaeology, geology, and environmental studies.


The basic principle of GPR is that it emits electromagnetic waves into the ground and measures the reflections or echoes that bounce back from subsurface objects or interfaces. The radar waves can penetrate different materials, such as soil, rock, concrete, or asphalt, and reflect off boundaries between different materials or objects.


GPR systems typically consist of a control unit, an antenna, and a display screen. The antenna is the main component that emits and receives the radar waves. The control unit controls the radar signal and processes the received signals to create an image or profile of the subsurface. The display screen shows the real-time data and allows the user to interpret the results.

A digital rendering of the rebar inside a concrete slab

GPR can provide valuable information about the subsurface, including the depth and location of objects, the thickness of layers, and the presence of voids, cracks, or other anomalies. It can be used to detect and locate PT cables, conduits, rebar, underground utilities, buried structures, archaeological artifacts, geological features, and more.


GPR is a non-destructive testing method, meaning it does not require drilling, excavation, or damage to the surface being investigated. It is a versatile and efficient tool for subsurface imaging and has become an essential technique in many industries.

Why Should You Call for a GPR Investigation Before Cutting?

Starting work on pre-existing concrete structures is difficult to plan, as various materials can be hidden inside any given slab. These obstacles, such as pipes and rebar, must be located before work can start.


Cutting concrete blindly can result in personal injury, or costly damage to the property. To avoid the risk of injury, x-ray machines have traditionally been employed to scan the inside of concrete slabs in order to map its contents. However, this process is slow, clunky and potentially unsafe due to the radiation the x-ray machine generates. A far better alternative is the “GPR” system like the one used by Cobra Concrete, the premiere Chicago concrete scanning service.

  • Safety

    GPR helps identify and locate any hidden utilities or objects beneath the concrete surface, such as electrical cables, gas lines, water pipes, or rebar. Cutting into these utilities can cause serious accidents, injuries, or damage to infrastructure. GPR allows for the detection and avoidance of these hazards, ensuring the safety of workers and preventing costly repairs.

  • Cost-Savings

    Accidentally cutting into utilities or objects can result in expensive repairs, delays, and legal liabilities. By using GPR to locate and mark the position of these utilities before cutting, potential damages can be avoided, saving both time and money.


  • Efficiency

     GPR provides real-time, non-destructive scanning of the subsurface, allowing for quick and accurate identification of potential obstacles. This helps contractors plan their cutting or excavation activities more efficiently, reducing downtime and improving project timelines.

  • Accuracy

    GPR can provide detailed information about the depth, size, and location of objects beneath the concrete surface. This allows contractors to make informed decisions about the best approach for cutting or excavating, minimizing the risk of errors or damage.

  • Compliance

     In many job sites, it is a legal requirement to use GPR or similar technologies to locate utilities before cutting or excavating. By following these regulations, contractors can avoid penalties, legal issues, and damage claims.

Overall, using GPR before cutting concrete is essential for ensuring safety, minimizing costs, improving efficiency, maintaining accuracy, and complying with regulations. It is a proactive measure that helps prevent accidents, damages, and disruptions during construction or renovation projects.

A Ground Penetrating Radar (GPR) survey is conducted using the following steps:

  • Equipment Setup

    The GPR system consists of a control unit and a radar antenna. The antenna is connected to the control unit, and the system is powered on.

  • Calibration

     Before starting the survey, the GPR system is calibrated to ensure accurate data collection. This involves setting the appropriate parameters such as dielectric constant, time and linear gain, and background removal depth.


  • Data Collection

    The radar antenna is placed on the ground and moved along the survey area in a systematic pattern. The antenna emits electromagnetic waves into the ground, and the reflected signals are recorded by the system. The data is collected in the form of radargrams, which are cross-sectional images of the subsurface.

  • Data Interpretation

    The collected data is analyzed and interpreted to identify subsurface features and anomalies. This involves examining the amplitude, shape, and depth of the reflections to determine the presence of underground objects or structures.

  • Mapping and Reporting

    The interpreted data is used to create field markings, showing the location and characteristics of the detected features. A report is generated, summarizing the findings and providing recommendations if necessary.

It is important to note that conducting a GPR survey requires expertise in data interpretation and knowledge of the subsurface conditions. Professional geophysicists or surveyors are typically involved in performing and analyzing GPR surveys.

A spray painted grid of the underground utilities found with GPR scanning
A room with a lot of red and white tape on the floor to show where the underground utilities are found.

gpr concrete scanning applications

Common GPR (Ground Penetrating Radar) concrete scanning applications include:

  • Construction and Renovation

    GPR scanning is essential during construction and renovation projects to locate rebar, post-tension cables, and other embedded objects within concrete structures. This helps avoid accidental damage during drilling, cutting, or excavation.

  • Utility Detection

    GPR is used to identify underground utilities like water pipes, gas lines, electrical conduits, and sewer systems. This is crucial to prevent utility strikes, ensuring worker safety and minimizing service disruptions.


  • Bridge and Road Inspection

    GPR is employed to assess the condition of bridges and roads by detecting voids, delamination, and subsurface defects within the concrete. This helps prioritize maintenance and repair efforts.

  • Concrete Slab Thickness Measurement

    GPR can determine the thickness of concrete slabs, which is useful for assessing the structural integrity of floors, pavements, and parking lots.

  • Historical Preservation

    In historical restoration projects, GPR is used to assess the condition of old structures, detect hidden architectural elements, and plan restoration work without damaging the original materials.

  • Environmental Site Assessments

    GPR is used in environmental assessments to detect underground storage tanks, soil anomalies, and contaminants. This aids in site characterization and remediation efforts.

  • Cemetery Mapping

    GPR is employed to map burial sites in cemeteries, identifying unmarked graves and assisting in cemetery management and expansion.

  • Geological and Geotechnical Studies

    GPR helps geologists and geotechnical engineers study subsurface conditions, including bedrock depth, soil stratigraphy, and groundwater levels.

  • Archeological Surveys

    GPR is utilized in archeology to detect buried artifacts, structures, and archaeological features without excavation.

  • Concrete Quality Assessment

    GPR can assess concrete quality by identifying voids, honeycombing, and poor consolidation, aiding in quality control during construction.

These applications showcase the versatility of GPR concrete scanning in various industries, ensuring safety, efficiency, and accurate decision-making in projects involving concrete structures.

subsurface features gpr can detect

Ground Penetrating Radar (GPR) concrete scanners can identify a range of items and features within concrete structures. Some of the most common items and features that GPR can detect include:

  • Rebar

    GPR is highly effective at locating reinforcing bars (rebar) embedded within concrete. It can determine the depth, spacing, and orientation of rebar, which is crucial for construction and renovation projects.


  • Post-Tension Cables

    GPR can detect the presence and layout of post-tension cables in concrete slabs and beams, helping avoid damage during drilling or cutting activities.


  • Conduit and Pipes

    GPR is used to locate electrical conduits, water pipes, gas lines, and other utility conduits embedded within concrete structures. This prevents accidental damage and ensures safety.

  • Voids and Delamination

    GPR can identify voids, gaps, and delamination within concrete, which may indicate structural defects or deterioration.

  • Thickness of Concrete

    GPR can measure the thickness of concrete slabs and determine variations in thickness, which is valuable for assessing structural integrity.


  • Cracks and Fractures

    GPR is capable of detecting cracks, fractures, and discontinuities in concrete, aiding in condition assessment and maintenance planning.

A live digital rendering of what's inside a concrete slab.

Service Specs:

Depth

Up to 16"-36" depending on site conditions

Type of Cut

Typical Depth Penetration

Materials Cut

Concrete, Rebar

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gpr concrete scanning FAQs


We've compiled this comprehensive list of frequently asked questions to provide you with quick and informative answers. Whether you're a new customer seeking information about our offerings or a returning customer with inquiries about using our platform, you'll find valuable insights here.

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  • How deep can you see into concrete?

    The antennas Cobra use can penetrate up to 18″ thick concrete on applications with both sides accessible by up to 36″.

  • Is GPR Safe?

    Absolutely. Much like ultrasound, the signals are very high frequency not unlike those of Wi-Fi or cellphones. The equipment is FCC approved and deemed safe for the operator and all persons nearby. It is much safer AND cost effective than X-ray inspections.

  • How Accurate Is GPR?

    On an average 6″ – 8″ slab on grade inspection, targets were located within 1/4″ of their markings laterally and within 1/4″ of their depth estimations. Markings are made as bold and clear as possible unless finished surfaces do not allow. If that is the case, other means are used such as masking tape, pencil, etc.

  • Why is GPR scanning important in construction projects?

    GPR scanning is crucial for locating rebar, post-tension cables, and utilities within concrete, helping to prevent accidental damage, ensure safety, and save time and money during construction.


  • Is GPR scanning effective for assessing the condition of concrete structures?

    Yes, GPR can identify voids, delamination, cracks, and other structural defects, aiding in condition assessment and maintenance planning.

  • How long does a typical GPR scanning project take?

    The duration of a GPR scanning project depends on the size and complexity of the structure. Small projects may take a few hours, while larger ones could take several days.

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