What is Ground Penetrating Radar? Our GPR survey expert Chris talks through everything you need to know about Ground Penetrating Radar scanning, including the purpose and applications of these surveys, along with the advantages and limitations that come with this surveying method.

GPR is a non-intrusive method of detecting sub-surface objects. It uses radio-waves to create an image of the sub-surface which in turn is used to determine the underground landscape of a target area. It’s used when intrusive methods such as excavation are not viable to give an initial overview of what lies beneath the surface. It’s key applications are Utility detection, in Archaeological situations and other construction-related scenarios. It’s a key method in compliance with the UK industry standard PAS128 specification, alongside Electromagnetic location as a minimum.

GPR works using a single or multi-channel antenna to send radio pulses downwards into the ground and then receives a return signal. Depending on the composition of the medium, the transmitted waves travel at different speeds, and when they interact with an object they’ll be reflected depending on what that object is. The receiving element of the antenna will then pick up this reflection and then the software will turn this into a usable image. A surveyor will then analyse this data and plot the results in an agreed format.

Read more: The Insiders Guide To GPR

Ground Penetrating Radar or GPR is used when the location of underground features on a particular site or area is a key requirement of a particular project. This is usually when ground is to be broken – particularly in construction projects for example. On any project where an understanding of the sub-surface landscape – be it utilities or other sub-structure – is required, the deployment of GPR should be considered. However, the use of GPR as a sole method of detection would never be recommended by an industry professional.

Read More: What Is A GPR Survey?

Ground Radar is very much a passive method. It doesn’t definitively identify a particular service as such, rather it confirms the presence of ‘a feature’. The skill in determining what that feature might be is then down to the surveyor analysing the data, and it’s not always possible unless there is supporting evidence either locally (on-site) or in record form. In some cases the best result you can achieve is actually determining there is ‘something’ in that particular location and advising that more intrusive techniques might be employed to resolve whether it’s presence impacts any design or groundworks. Ground conditions also limit effectiveness – so dry, light sandy soils for example make excellent media for Ground Radar scanning whereas results will be less comprehensive in heavy saturated soils, ‘made’ ground or through reinforcement.

Unlike electromagnetic location (EML), which struggles with non-conductive materials, GPR has the ability to locate both metallic and plastic utilities, fibre‑optics, drainage, voids, and more with accurate depth readings. That makes it an essential tool, alongside EML for safe excavations and precise site planning.