GPR utility detection before excavation: how it works and what to expect
Hitting a buried cable or pipe stops work, costs money and can injure people. Ground penetrating radar (GPR), used together with electromagnetic locators, finds and maps buried utilities before digging starts.
IllustrationThe short answer
A utility survey starts with existing records, then sweeps the area with electromagnetic locators for metallic services and scans it with GPR in a grid to find metallic and non-metallic pipes, ducts and voids. The findings are marked on the ground, surveyed and delivered as a utility map, and critical crossings are confirmed with trial pits. Results depend on soil: dry, sandy ground suits GPR better than wet, clayey or saline ground.
How GPR works
GPR sends radar pulses into the ground and records the reflections from changes in material, such as a pipe, a cable duct, a void or a layer boundary. Buried objects usually appear as hyperbolas in the radar image. GPR detects plastic and concrete pipes that electromagnetic locators miss, which is why the two methods are used together.
What affects the results
- Soil: dry sand and gravel let the signal travel deeper; wet clay and saline ground absorb it and reduce depth.
- Antenna frequency: higher frequencies show more detail near the surface, lower frequencies reach deeper.
- Surface: reinforced concrete and dense fill can mask what lies below.
- Size and depth: small or deep services are harder to detect than large, shallow ones.
The survey step by step
- Collect existing utility records and drawings.
- Sweep with electromagnetic locators, applying signals to accessible services where possible.
- Scan with GPR along a grid of lines across the area.
- Mark the findings on the ground with the agreed colour code.
- Survey the marks with GNSS or a total station and produce a CAD or GIS utility map with depths where available.
- Confirm critical crossings with trial pits before excavation.
Survey quality levels
Many projects describe the reliability of utility information with the quality levels of the ASCE 38 standard: from QL-D (records only) and QL-C (records plus visible features), to QL-B (services detected and mapped with GPR and electromagnetic locators) and QL-A (exposed and measured in trial pits). Stating the required level in the scope avoids surprises.
How YAZ Development helps
YAZ Development provides GPR and geophysical surveys and underground utility detection in Saudi Arabia, delivering surveyed utility maps ready for design and GIS. YAZ carried out ground penetrating radar surveys to detect underground utilities at Qiddiya, and underground utility detection in the early stages of NEOM.
Last updated: 20 October 2026 · YAZ Development
Common questions
How deep can GPR see?
It depends on the soil and the antenna. In dry, sandy ground GPR can reach a few metres; in wet, clayey or saline ground the depth is much less. A site test is the best guide.
Does GPR find plastic pipes?
Often yes, because it detects changes in material rather than metal. Electromagnetic locators cannot find plastic pipes unless a tracer wire is present, which is why both methods are combined.
Do I still need trial pits after a GPR survey?
For critical crossings and where depth must be certain, yes. GPR and locators map the services; trial pits confirm their exact position and depth.
More guides
- How to set up survey control on large construction projects in Riyadh Establish a primary network of stable monuments, observed with static GNSS and tied to the Saudi national reference frame (KSA-GRF17), adjust it by least squares, then densify it with total station traverses and precise levelling close to the work areas.
- Construction surveying and setting-out for infrastructure projects in Saudi Arabia Construction surveying transfers the design onto the ground and checks the result: it covers control checks, setting-out of alignments and structures, levels, as-built surveys and survey records for quality control.
- How accurate is 3D laser scanning for construction, and how to choose a provider Modern terrestrial scanners measure single points to a few millimetres at short range, but project accuracy depends on registration, ties to survey control, range and surface.
- How structural monitoring keeps excavations safe on Saudi infrastructure projects Before digging starts, a baseline is measured on the retaining walls, the ground and nearby buildings.
- The benefits of GIS in large-scale urban development in Saudi Arabia GIS gives a large development one shared, location-based source of truth: survey, drone, utility, design and asset data in a single coordinate system.
- Scan to BIM vs a traditional measured survey: which one does your project need? A traditional measured survey records selected points and dimensions and suits simple spaces and small scopes.
Need Professional Surveying Teams or Geospatial Engineering Services?
Message us on WhatsApp or call +966 50 298 0251