GPR Utility Survey
Why GPR is the second detection method, what it finds that a locator cannot, and where it struggles.
What the locator cannot hear.
Why GPR is the second method
An electromagnetic locator only finds what it can energise or what carries a signal. Ground-penetrating radar finds changes in the ground itself, so it is the second method that PAS 128 Type B requires. We run a Proceq GS8000, a stepped-frequency GPR from 40 to 3,440 MHz with built-in multi-band GNSS.
What it finds that a locator cannot
Plastic pipes and ducts, clay drainage, voids and chambers, and abandoned services that no longer carry a signal.
Where it struggles
Wet clay, which absorbs the signal. Made ground, which scatters it. Reinforced slabs, which mask what is beneath them. The drawing states what could not be detected as well as what was.
Why GPR alone is not PAS 128
PAS 128 Type B needs two detection methods and a full passive sweep. GPR on its own is a useful survey, but it is not a PAS 128 survey.
Who does it
Our utility surveyors hold the ProQual Level 3 Certificate in Utility Mapping and Surveying and deliver surveys to PAS 128:2022.
Where it helps
- Before excavation, piling, trenching or ground anchors
- Before a basement dig or a pavement opening in a London street
- Where the statutory records are old, incomplete or contradict each other
- On a site with a history of services being added and abandoned
- When the client or principal designer has specified PAS 128
- Before EV charger, district heating or substation works
What you receive
- Marked-up ground in survey paint, colour-coded by service
- Utility drawing in DWG/DXF and PDF, each line labelled with type and PAS 128 quality level
- Report stating survey type, methodology, kit, operator qualification and limitations
- Records pack from the Type D search
- Within 5 working days of the site visit
A note on interpretation. A PAS 128 survey records what was detected to the stated quality level. It does not guarantee that every service has been found. Safe digging practice, trial holes where the drawing says QL-B3 or B4, and HSG47 still apply.
Often surveyed together.
GPR Concrete Scanning
Ground penetrating radar finds rebar, post-tension cables, conduits, and voids hidden inside concrete, before they become a problem.
Learn moreFerro Scanning
Electromagnetic scanning to map reinforcement, measure cover depth, and estimate bar diameter without touching the concrete.
Learn moreMore from PAS 128 Utility Surveys.
- PAS 128 Utility SurveysPAS 128 Explained
The British specification for finding and recording buried utilities, in plain English.
- PAS 128 Utility SurveysType B Detection Survey
Two detection methods over the whole area, every service positioned and labelled with how confident we are.
- PAS 128 Utility SurveysCAT and Genny Survey
A quick electromagnetic sweep for energised cables and metallic pipes, honestly described.
Got a dig coming up?
Send drawings, photos or proposed fixing locations and we'll advise the right survey approach.