GPR Detection Rates & Underground Utility Survey Statistics 2026
How well does ground-penetrating radar actually find what's buried, and what does missing it cost? We pulled together widely cited figures on GPR detection rates, accuracy, depth and the price of getting it wrong, every number attributed to a named source.
Detection accuracy & PAS 128
GPR accuracy in the UK is framed by PAS 128, the survey standard that grades every located service by how it was found and how much you can trust its position.
| Quality level | How it's found | Confidence / accuracy |
|---|---|---|
| QL-D | Desktop records search only | Lowest confidence, existing utility records, no site survey |
| QL-C | Site reconnaissance | QL-D data reconciled with visible surface features |
| QL-B | Geophysical detection (GPR + EML) | From plan ±150 mm and depth ±15% (QL-B1) to undefined (QL-B4, suspected but not detected) |
| QL-A | Physical verification (e.g. trial hole) | Service exposed or observed and surveyed in place, ±50 mm |
Source: PAS 128:2022 (BSI), as summarised in the TSA PAS 128 Client Guide. Sub-level tolerances vary; confirm against the standard for design use.
- ±50 mm: horizontal and vertical tolerance of a QL-A line, where the service is physically verified and surveyed in place. (Source: TSA PAS 128 Client Guide)
- 5–9 cm: calculated vertical resolution of a 250 MHz antenna, assuming sandy soils with clay and silt. (Source: Karsznia, Onyszko & Borkowska, Sensors (MDPI), 2021)
Ground conditions & what limits detection
The single biggest control on GPR performance is the ground itself. Electrical conductivity, driven mostly by clay content and moisture, attenuates the radar signal and sets the realistic depth limit.
- < 1 m: penetration in conductive clays or materials with conductive pore fluids. (Source: US EPA CLU-IN)
- < 10 m: typical penetration in most soil and rock. (Source: US EPA CLU-IN)
- Up to ~30%: potential depth-estimation error, even over 0.5 m, when assumed soil properties don't match conditions, for example after rain. Measured on a sandy soil. (Source: Curioni, Chapman & Metje, Journal of Applied Geophysics, 2017)
- Attenuation of the EM wave, controlled by subsurface electrical conductivity, is the principal factor limiting GPR investigation depth. (Source: US EPA CLU-IN)
Depth and resolution by antenna frequency
GPR antennas trade depth against detail: higher centre frequencies resolve smaller targets but penetrate less, while lower frequencies reach deeper at coarser resolution. Real depths are often far lower in wet or clay soils.
- 250 + 700 MHz: the dual centre frequencies used by a common utility-detection GPR (Leica DS2000). (Source: Hexagon / Leica Geosystems)
The cost of not detecting
The case for surveying rests on what happens without one. A key UK dataset comes from University of Birmingham research analysing thousands of real strikes.
- 3,348 incidents from nine organisations were analysed in a major UK strike study. (Source: Metje, Ahmad & Crossland, ICE Proceedings. Municipal Engineer, 2015)
- £2,800: average repair cost for a fibre-optic strike, the highest of the utility types in that study. (Source: Metje et al., U. Birmingham, 2015)
- 0.5% of construction cost bought QL-A/QL-B data and produced 1.9% construction savings across 71 highway projects. (Source: US FHWA / Purdue, 1999)
- $206 : $1 the best single-project return; only 3 of 71 projects had a negative ROI. (Source: US FHWA / Purdue, 1999)
- 3.86 million safe-digging searches passed through the LSBUD portal in 2024. (Source: LSBUD Digging Up Britain, 2025)
UK safe-digging search share by sector, 2024. Source: LSBUD Digging Up Britain report, 2025. Telecoms 37.5% (1,444,280 searches), water 27.5%, local authorities 11.4%.
Concrete scanning detection
Inside concrete, GPR locates reinforcement, post-tension tendons, conduits and voids before anyone cuts or cores.
- 300–400 mm: approximate slab thickness in which a 2.0–2.6 GHz antenna detects small targets such as rebar and small conduit. (Source: SPH Engineering)
- ±¼ inch (≈6 mm): accuracy to the centre of located objects claimed by US scanning firm GPRS, with depth to ±10–15%. (Source: GPRS)
GPR vs other detection methods
No single method finds everything. The reason competent surveys pair GPR with electromagnetic location, and verify with vacuum excavation where it matters, is that each covers the others' blind spots.
| Capability | GPR | EM locator | Vacuum excavation |
|---|---|---|---|
| Detects metallic pipes/cables | Yes | Yes | On exposure |
| Detects plastic / non-metallic | Yes | No (needs tracer) | On exposure |
| Estimates depth | Yes | Limited | Exact (exposed) |
| Non-destructive | Yes | Yes | Yes (air/water) |
| Degraded by wet clay | Yes | Less affected | No |
Source: HSE HSG47. EM locators cannot find non-metallic pipes without a tracer wire.
The UK safe-digging framework, HSE's HSG47, sets out a three-element safe system of work: plan, locate and identify, then dig safely. GPR sits squarely in the middle step. (Source: HSE HSG47, 3rd ed.)
Market size & growth
Market-research firms size these markets very differently, so each figure is attributed to the firm that published it rather than blended into one number.
- $0.53bn (2026) → $0.92bn by 2032 (9.6% CAGR): the GPR market. (Source: MarketsandMarkets)
- $1.38bn (2024) → $3.30bn by 2032 (11.5% CAGR): underground utility mapping. (Source: Data Bridge Market Research)
Estimates vary widely across providers and are revised often. Treat each as "as reported by" its source.
Frequently asked questions
How accurate is GPR for locating buried utilities?
Under PAS 128, a service detected geophysically gets a Quality Level B grade. The best of these, QL-B1, carries a tolerance of ±150 mm in plan and ±15% of its depth; lower QL-B grades are wider or undefined. The highest level, QL-A (±50 mm), needs the service to be physically exposed or observed in a chamber.
How deep can GPR detect underground?
It depends almost entirely on the ground. In conductive clays, penetration can fall below one metre, and even in most soil and rock it is commonly less than ten metres (US EPA CLU-IN). Higher antenna frequencies give better resolution but shallower depth; lower frequencies reach deeper at coarser resolution.
Can GPR find plastic pipes?
Yes. Because GPR responds to changes in dielectric properties rather than metal, it can detect non-metallic services such as PVC, clay and asbestos-cement pipes. Electromagnetic locators cannot find these unless a metallic tracer wire is present, which is why a competent utility survey uses both methods together.
How many utility strikes happen in the UK each year?
A widely reported industry estimate, used by the government's Geospatial Commission in its NUAR economic case, puts UK utility strikes at around 60,000 a year. University of Birmingham research found that telecommunications and electricity cables were the most commonly damaged services.
Does surveying before you dig actually save money?
The evidence says yes. A US Federal Highway Administration / Purdue study of 71 projects found $4.62 saved for every $1 spent on subsurface utility engineering. A University of Birmingham study of 16 UK strikes put the ratio of indirect and social costs to direct repair cost at about 29:1, so the true cost of a strike is far higher than the visible repair bill.
Sources
US Federal Highway Administration (Purdue SUE study); Metje, Ahmad & Crossland, ICE Proceedings (Municipal Engineer), 2015; Makana et al., ICE Infrastructure Asset Management (University of Birmingham); Curioni, Chapman & Metje, Journal of Applied Geophysics, 2017; US EPA CLU-IN; UK Health and Safety Executive (HSG47); Geospatial Commission, NUAR economic case summary; LSBUD Digging Up Britain 2025; PAS 128:2022 (BSI); TSA PAS 128 Client Guide; Karsznia et al., Sensors (MDPI), 2021; Hexagon / Leica Geosystems; SPH Engineering; GPRS; MarketsandMarkets; Data Bridge Market Research. Figures are quoted as reported by each source and were current at the time of writing (June 2026).