GPR Surveys

A Ground Penetrating Radar (GPR) Survey is a non-invasive technique that uses pulses of energy to identify objects underground. The results of a GPR survey are used to create an underground utility survey.

GPR Surveys

What is a GPR survey?

A GPR survey is a technique that uses radio waves to take images of objects below the ground without the need to dig up the soil. 

As the surveyed area gets deeper, the quality of the captured images decreases. The setup of a GPR system varies depending on the intended purpose of use.

GPR surveys are carried out in various environments such as car parks, gardens, derelict land, basements and churches. They are usually commissioned by construction workers.

GPR Surveys

What can a GPR detect?

GPR can detect metallic and non-metallic underground utilities such as gas, electrical, telecommunications and water. Specific objects commonly detected include pipes, wiring and fiber optics. Surveys can also reveal changes in soil profiles, air pockets, rocks and other geological features. Furthermore, GPR technology can identify sinkholes and salt water infiltration, and assess ice thickness.

Benefits

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Highly accurate

GPR surveys gather detailed, accurate information as they can detect metallic and non-metallic objects. The data can be interpreted in real-time or processed off-site by the surveyor.

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Cost-effective

Opting for a GPR survey means you know exactly what you’re up against underground. This allows for proper planning of any construction or groundwork which prevents delays and minimises the risk of structural damage – saving time and money.

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Fast data collection

Measuring the signals from the radar is simple and the image is produced in a matter of minutes, making it suitable for scanning large areas. GPR is also faster, safer and cheaper than radiography.

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Non-destructive and safe

It is a non-invasive method – all you need is single-sided access to the ground, making it ideal for public spaces.

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High-resolution images

Both high and low frequencies are used to gather high resolution images and different depths.

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Variety of applications

GPR surveys are versatile and can be used in numerous environments.

The Process

To complete a GPR survey, a high-frequency electromagnetic pulse is sent into the ground using a transmitter. The radar signals are reflected back and detected by the antenna. Next, the signals are processed and displayed on a graphic recorder. The transmitter and antenna will be moved across the area of interest and the graphic recorder will create a final radar image.

The GPR technique is used as standard to complement our underground utility surveys and service avoidance surveys as they give spatial context and provide other useful evidence.

GPR Surveys

GPR Resolution

Resolution refers to the smallest target that GPR can detect, and the ability to identify and differentiate between two separate targets. The resolution depends on the size of the wavelength of the signal, and the size of the wavelength depends on the frequency of the signal. Lower frequency antennas transmit larger signals, while higher frequency antennas transmit smaller signals. 

High frequency antennas offer a better resolution however, the signal cannot penetrate as deep. Lower frequencies are able to reach further underground, but they are less able to identify different features and smaller objects. 

Our surveyors are experienced and can use a combination of frequencies to produce accurate, reliable results.

What to Expect

When you opt for a GPR survey with us, you will receive an annotated drawing of the object’s location and a written report. Your surveyor will interpret what the underground objects are based on the radar signals. Note that the GPR can’t see through objects. For example, if you have a large pipe placed above a smaller pipe, it’s less likely that the smaller pipe will be detected.

Applications to the construction industry

Our surveys are popular amongst professionals in the construction industry, and they are a common step before groundwork is completed. Some specific applications include:
GPR Surveys

Used to determine the general construction such as the material type used, the location of structural steel and layer thickness.

GPR Surveys

GPR works on thin concrete floors, roads, pavements, walls, tunnels and balconies to locate and map rebar, tendons and conduits. The radar image is clearer and can reach deeper than the majority of other surveys.

GPR Surveys

Even more specifically, slab thickness and reinforcement distribution can be identified. Voids below the slabs can be highlighted, depending on the thickness of material, which is important to resolve before a failure occurs; this is typical for busy areas like warehouses and factories.

GPR Surveys

GPR may also be used to spot the location of a chimney flue due to the change in the material of the masonry wall and the flue void.

GPR Surveys

This application is common in listed buildings as the radar is non-intrusive.

GPR Surveys

As well as identifying pipes and storage tanks, the survey can detect any leaks and contamination.

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GPR Surveys

Why Midland Survey?

We are part of the European GPR Association which is an association for users and manufacturers of GPR equipment. This association is committed to raising the standards in the GPR industry. When you choose Midland Survey for your GPR survey, you can be confident that we follow all industry standards. 

Our team of professionals have many years of experience working with GPR, offering a personalised experience to each case. We use the latest technology to produce images that are detailed and accurate. Our surveys are used in various sectors such as construction, demolition and archaeology. 

Midland Survey has offices in Southam, Stroud, Leeds, Horsham and Milton Keynes and we provide our services anywhere in the UK.

FAQs

The average cost of a GPR survey is between £500 and £1000  per day. The cost will depend on the size of the area being surveyed and the equipment used. At Midland Survey, we are transparent about our pricing and offer competitive rates. Get a quick quote or chat with one of our experts about your project.

A GPR survey can usually be undertaken and completed within a day on site, although this will vary depending on the size of the area being assessed.

The depth of a GPR survey depends on the material being surveyed. It can reach depths of up to 5 metres in low conductivity materials like dry sand and granite. For high conductivity materials such as moist clays and shale, the depth is around 1 metre or less. This is because higher conductivity materials may absorb GPR signals.

Although nothing can be 100% accurate, with the right conditions, GPR surveys can be at least 90% accurate. The accuracy can be affected by the type of soil being scanned. The soil moisture and soils that contain high levels of salt and minerals like clay soils can hinder the GPR reading.

GPR is a great technique for scanning through concrete, depending on the thickness. It is effective on most materials such as rock, soil, ice, fresh water and concrete.

We use Leica DS2000 and Proceq GS8000 GPR kits. They both self-calibrate before every job and utilise their own bespoke processing software.

If you like the look of our work and have an upcoming project in mind, get in touch. We can advise you on the type of survey you need and execute it with complete precision.