GPR rebar mapping, reinforcing steel location and concrete imaging surveys to depths of up to 400mm. The high-resolution data is far superior to that offered by most other techniques.

Site reinforcement surveys

We use Ground Penetrating Radar (GPR) for rebar mapping and concrete imaging surveys. The surveys are nonintrusive and cause minimal disruption. They can be conducted in vacant or occupied buildings.

Site surveys are undertaken by our trained and experienced GPR surveyors. Depending on survey requirements and access, scanning is undertaken on a regular orthogonal grid or standalone scans as required. Typically, the collected site data is analysed off-site, meaning that the site data collection is quick and efficient.

A high-resolution GPR antenna in a schematic representation of two reinforcement layers in concrete.
High-resolution rebar mapping using GPR

A GSSI SIR 3000/4000 GPR control unit is generally used with a high-frequency antenna (typically in the range 2600 MHz to 1600 MHz). The 2.0 GHz Palm antenna is very compact and particularly useful for scanning small areas where access is restricted.

The compact high-resolution 2.0 GHz GSSI Palm high-frequency antenna.
The 2.0 GHz GSSI Palm high-frequency antenna is very compact and allows scanning to within 45 mm of an obstruction.

Locating deep reinforcing steel

The location of deep reinforcing steel (rebar) in reinforced concrete can be difficult. Cover meters and the Hilti Ferroscan are typically limited to approximately 100 mm. GPR offers major advantages for locating deep-reinforcing steel:

  • High-resolution scans to detect rebar up to 400 mm deep
  • Lower antenna frequencies to detect deeper rebar
  • Locate deep rebar, orientation and depth of cover
  • Rebar can be located in real-time
  • GPR scan data can be saved for off-site analysis, including CAD plotting

Ground Penetrating Radar can be used with different antenna frequencies to provide a range of penetration depths and resolutions. A higher-frequency antenna (typically in the range of 2600 MHz to 1600 MHz) provides high resolution and depth penetration up to 400mm. Lower frequencies provide greater depth penetration, but at a lower resolution and may not be able to resolve individual bars.


Rebar mapping, reinforcing steel location and concrete imaging results can be plotted in CAD, presented on annotated radargrams (cross-section view), depth slices (plan view – see example below) or on sketches.

A radargram image showing a section view through a slab/beam with detected features indicated (as described in the caption).
A radargram image showing a section view through a slab/beam. The dashed pink line indicates a screed/concrete interface, the top rebar is highlighted by red dots, the bottom rebar is highlighted by green dots, the underside of the slab is indicated by the solid yellow line and the down-stand beam by the dashed yellow line.

The advantages of GPR rebar surveys

Ground Penetrating Radar (GPR) detects changes in the sub-surface, so it is not limited to detecting reinforcement or metallic objects. It can be used to provide immediate results on-site, or the data can be saved electronically and analysed off-site to provide detailed results such as high-resolution rebar mapping.

High-resolution rebar mapping is possible to depths up to 400mm using a high-frequency antenna. Lower antenna frequencies provide greater penetration depth, albeit at a lower resolution.

Ground Penetrating Radar can:

  • Detect metallic and non-metallic objects and features
  • Map rebar distribution
  • Can resolve two layers of reinforcement
  • Detect voids
  • Identify changes in construction
  • Determine slab thickness
  • Requires access to one side only

The results from our GPR Concrete Imaging Surveys can be used to confirm as-built drawings, determine reinforcement details when drawings are unavailable, and conduct structural assessments. It is also suitable for locating rebar and tendons before cutting, core, or drilling.

Need more information?

Contact us

Contact us to find out more about our GPR rebar mapping and concrete imaging surveys and how we can help you:

Tel: 0207 565 7056

Information sheet

Download our information sheets about GPR rebar mapping and concrete imaging surveys.

Are you wondering what else GPR can be used for? GPR surveys can investigate the subsurface and detect unseen features. Learn more about our most popular GPR surveys.