Application Guide
Geophysical Equipment for UXO Detection
Unexploded ordnance surveys rely on magnetometry and time-domain electromagnetics to find buried munitions before construction, dredging, cable laying or land reuse.
UXO survey is a risk-reduction exercise: the aim is to detect and position every potentially hazardous item down to the clearance depth required for the project. Ferrous ordnance distorts the Earth's magnetic field, which makes high-sensitivity magnetometers and gradiometers the primary tool; time-domain EM adds detection of non-ferrous metallic items and helps discriminate targets.
Survey design — line spacing, sensor height and positioning accuracy — matters as much as sensor choice. Most projects use multi-sensor arrays with RTK GNSS so that every anomaly can be reacquired and investigated.
Methods Compared
| Method | Detects | Typical Depth | Limitations |
|---|---|---|---|
| Caesium / optically pumped magnetometers | Ferrous ordnance, buried steel | Depends on item size — larger bombs detectable at several metres | Blind to non-ferrous items; sensitive to nearby steel and geology |
| Fluxgate / vertical gradiometers | Ferrous items, shallow ordnance | Shallow to moderate | Lower sensitivity than optically pumped sensors, but robust and cheaper |
| Time-domain EM (e.g. EM61-class) | All metals incl. aluminium and copper | Typically shallower than magnetometry for large items | Shorter range; more sensitive to surface clutter |
| Marine towed magnetometers | Seabed and buried ordnance offshore | Dependent on sensor altitude above seabed | Needs low, stable tow altitude and good positioning |
Depths are typical field values — actual performance depends on ground conditions, target size and survey design.
Land, near-shore and offshore
On land, hand-carried or cart-mounted multi-sensor arrays are standard. Offshore cable routes and wind-farm sites use towed magnetometers and gradiometers flown close to the seabed, often combined with side-scan sonar. Drone-borne magnetometers increasingly provide fast reconnaissance on difficult terrain before detailed ground survey.
Target discrimination
Clutter from scrap metal, foundations and geology is the main cost driver in UXO projects. Combining magnetic and EM data, recording dense, accurately positioned data and using a dedicated anomaly-classification workflow reduces the number of targets that need excavation.
Recommended Instruments
A selection from our catalog. We source many more models — tell us what you need.
Which Condition Tier?
Because UXO survey results feed safety decisions, many clients specify New or Absolute Certified sensors with documented calibration. Refurbished sensors work well as array expansion or backup units; Surplus sensors are best kept for training and 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
Which is better for UXO, magnetometer or EM?
They are complementary. Magnetometers detect ferrous ordnance at greater depth; time-domain EM also detects non-ferrous metal and helps discriminate targets. Many specifications require both.
Can a magnetometer detect aluminium or brass items?
No — magnetometers only respond to ferromagnetic material. Time-domain EM instruments are used for non-ferrous items.
Do you supply marine UXO magnetometers?
Yes. We supply towed marine magnetometers and gradiometers in all four condition tiers, alongside our land magnetometer and EM range.
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