Application Guide
Geophysical Equipment for Utility Locating & Mapping
Ground penetrating radar and electromagnetic (EM) instruments find buried pipes, cables and ducts before excavation, and turn a site into a utility map that designers and contractors can trust.
Utility strikes are expensive and dangerous, and drawings are often incomplete. A non-intrusive survey combines two complementary physics: GPR images anything that contrasts with the surrounding soil — plastic, concrete and clay pipes as well as metal — while EM methods respond to metallic and conductive objects and can trace them over long distances.
Most professional utility surveys use both: EM to sweep for metallic services and conductive anomalies, GPR to confirm depth and to catch non-metallic services that EM cannot see.
Methods Compared
| Method | Detects | Typical Depth | Limitations |
|---|---|---|---|
| Ground penetrating radar (single-channel) | Metallic and non-metallic pipes, ducts, chambers, voids | Typically 0.5–3 m, less in wet clay | Penetration collapses in conductive clay and saline ground; needs line-by-line grids |
| Dual-frequency GPR | Shallow detail and deeper services in one pass | Typically up to a few metres | Same ground limits as GPR, but fewer passes needed |
| 3D array GPR | Full 3D utility maps over wide areas | Similar to single-channel GPR | Higher capital cost; most efficient on large or open sites |
| EM metal detection / time-domain EM | Metallic pipes, cables, buried metal | Typically up to 2–3 m for larger targets | Blind to plastic and clay; nearby fences and vehicles interfere |
Depths are typical field values — actual performance depends on ground conditions, target size and survey design.
Choosing between single-channel and 3D GPR
Single-channel and dual-frequency systems are the workhorses for day-to-day locating: quick to deploy, easy to interpret on screen, and enough for most trench-and-mark jobs. 3D arrays collect a full data volume in each pass and produce depth slices that show how services connect — the right tool for full-site utility mapping, road corridors and congested urban sites, where coverage per day drives the project cost.
Ground conditions matter more than the instrument
GPR performance depends on soil electrical conductivity. Dry sand and gravel allow deep penetration; wet clay, saline soil and slag fill can limit it to well under a metre whatever the antenna. A short test line before committing to a method is good practice — and the main reason survey firms keep both GPR and EM in their kit.
Recommended Instruments
A selection from our catalog. We source many more models — tell us what you need.
Which Condition Tier?
Utility survey firms often run a New or Absolute Certified primary system and add Refurbished units for extra crews. Superseded control units and antennas in Surplus condition are a low-cost way to add a frequency to an existing kit or to stock spares.
See the condition tier guide for what New, Refurbished, Absolute Certified and Surplus each include, or the industries overview for related sectors.
Frequently Asked Questions
Can GPR detect plastic pipes?
Yes. GPR responds to contrasts in electrical (dielectric) properties, so plastic pipes, especially water-filled ones, are usually visible. EM methods cannot detect plastic, which is why the two are used together.
How deep can utility GPR see?
In typical soils, utility GPR in the 250–800 MHz range sees roughly 0.5–3 m. Dry sandy ground allows more; wet clay or saline ground can limit it to less than a metre.
Do I need a 3D GPR array?
Not for routine locate-and-mark work. 3D arrays pay off on large or congested sites, full utility mapping projects and road corridors, where they cover far more ground per day and show how services connect.
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