Ground penetrating radar lets you see into the ground without digging it up. A GPR survey sends a radar pulse down into concrete, tarmac or soil and reads the reflections that come back, building a picture of what is underneath. 360 Surveys NI carries out GPR surveys across Northern Ireland and the Republic from our base in Portadown, using a Leica DS4000.
GPR can help investigate features that electromagnetic tracing may not detect, including non-metallic pipes and subsurface anomalies. Results depend on the material, depth, access and ground conditions. No survey can promise to detect everything.
What GPR can find
Buried services. Plastic and clay pipes that electromagnetic detection cannot pick up, alongside the metallic services it can. Usually run together as part of an underground utility survey, with the utility detection scope agreed to PAS 128:2022.
Reinforcement in concrete. Rebar, mesh, post tension cables and conduit, located before you core, cut or fix into a slab. The findings help the project team plan further investigation and safe working procedures.
Slab thickness and construction. How thick the slab is, how many layers, where the joints and voids sit.
Voids and sinkholes. Loss of ground beneath a slab, road or foundation, often the first physical evidence of a drainage failure or a solution feature.
Buried structures. Old foundations, tanks, culverts, wells and backfilled basements that no longer appear on any drawing.
The equipment
We use a Leica DS4000 for GPR work. The survey method is selected around the target, access and site conditions. Equipment capability alone does not guarantee the depth, completeness or accuracy of a particular survey.
For utility detection, GPR is used alongside electromagnetic location within the agreed PAS 128:2022 scope. The two techniques provide complementary evidence.
How a GPR survey works
A radar antenna is moved across the accessible survey surface. It transmits pulses and records the time each reflection takes to return. Where the pulse crosses a boundary between materials, a pipe wall, a rebar, the top of a void, part of the signal bounces back.
That return is processed into a cross section of the ground beneath the survey line. Run enough lines on a grid and the individual sections combine into a plan of what is down there.
The search coverage depends on the site and the investigation required. For utility work, we offer detection methods M1 to M4P under PAS 128:2022. The method and search resolution are agreed in the survey brief.
What you receive
- A marked up drawing in CAD or PDF showing what was found and where
- Targets painted on the surface where you need to work immediately
- Depth estimates, with the confidence attached to them stated honestly
- A short report covering the method used, the area covered and any ground conditions that limited the result
Typical turnaround is 6 to 10 working days from the site visit, depending on the size of the site and how many scans were captured.
What GPR cannot do
This matters more than the sales pitch. Radar is not an x-ray and anyone selling it as one is overselling.
Heavy wet clay, common across much of Northern Ireland, absorbs the radar signal and sharply reduces the depth you can reach. Saline ground near the coast does the same. Dense reinforcement in a slab can mask anything beneath it. Highly conductive made ground scatters the return.
Radar also shows you that something is there, not what it is. Interpretation is judgement based on the shape of the reflection, the depth, the context and the operator's experience. A good report distinguishes between what was positively identified and what is an anomaly of unknown cause.
Depths taken from radar are measured to the crown of the reflection unless stated otherwise, and in critical areas the only way to confirm what something is and exactly where it sits is a trial hole. We would rather tell you where confidence is low than hand over a drawing that implies more certainty than the method can give.
Concrete scanning before coring
This is one of the most common reasons people call. Someone needs a core hole or a chase through a slab and nobody can say what is in it.
Concrete scanning before coring helps investigate embedded features and inform the proposed drilling position. Coverage and limitations must be reviewed with the responsible project professionals before work proceeds. A scan is not a guarantee that an area is clear or authorisation to drill.
Void and sinkhole detection
Where a slab has settled, a road has dipped or a floor sounds hollow, radar can show whether there is a void beneath and roughly how far it extends. That turns a guess into something an engineer can design a remedy around, without opening up the ground first to find out.
Who uses GPR surveys
- Contractors coring or cutting a slab, or excavating near live services
- Structural engineers assessing an existing slab or investigating a settlement problem
- Civil engineers and utility companies mapping buried apparatus
- Architects working on an existing building with no reliable record drawings
- Developers carrying out clearance surveys before boreholes, piling or tree planting
What a GPR survey costs
It depends on the area, what you need found, how accessible the surface is and how densely the site needs to be searched. The amount of work depends on the investigation required. A full site grid survey takes longer and produces a lot more data to process.
Tell us the location, survey area, access arrangements and what you need to investigate. We can then discuss the scope and provide a site-specific quotation.
Where we work
We cover Northern Ireland from Portadown, including Belfast, Armagh, Craigavon, Newry, Lisburn, Banbridge, Dungannon, Ballymena, Coleraine, Omagh, Enniskillen and Derry, and we work across the border into the Republic including Dublin, Dundalk, Drogheda and Monaghan.
Working alongside other surveys
GPR is often one part of a larger piece of work:
- Underground utility surveys, where GPR runs alongside electromagnetic tracing to PAS 128
- Topographical surveys, so buried and surface detail sit on one coordinated drawing
- Measured building surveys where slab construction matters
- Drone surveys on larger sites
Frequently asked questions
What GPR equipment do you use?
We use a Leica DS4000. The survey method and achievable results depend on the target and site conditions.
How deep can GPR see?
Achievable depth depends on ground conditions, the target and the survey method. Wet clay, conductive ground and reinforcement can limit the signal. We discuss the site conditions and report limitations rather than promise a fixed detection depth.
How long does a GPR survey take?
Site time depends on the scope and access. Typical turnaround for the deliverables is 6 to 10 working days from the site visit, depending on site size and the number of scans.
Do you offer concrete scanning and void detection?
Yes. We offer concrete scanning before coring, plus void and sinkhole detection. Tell us the area, access and purpose so the appropriate scope and limitations can be discussed.
Will GPR find a plastic water pipe?
Often, yes, which is the main reason it is used alongside cable location. An empty plastic pipe in heavy clay is harder than a full one in gravel, so it is not guaranteed.
Do I need GPR or an electromagnetic utility survey?
For buried services, GPR and electromagnetic location provide complementary information and are used within the agreed utility survey scope. Concrete scanning and void investigations have different requirements. Tell us what you need to investigate so the appropriate method can be discussed.
Get a quote for your GPR survey
Tell us where the site is, roughly how big the area is and what you need to find. We will come back with a price and a date.
Request a quote or call 028 38339820.