Magnetometer measurements play an important role in detecting potential unexploded ordnance (UXO) below the surface. However, the CPT rig used to carry out these investigations can also influence the magnetic field being measured.

A magnetometer detects disturbances in the Earth’s magnetic field. It cannot automatically distinguish between buried ordnance and magnetic interference caused by the steel structure, hydraulic components or electrical systems of the CPT rig above it.

Understanding magnetic interference

The magnetic influence of a CPT rig can vary depending on its orientation, moving components, electrical activity and distance from the sensor. This interference is generally most noticeable near the surface and decreases as the magnetometer module is pushed deeper into the ground.

A consistent measurement setup is therefore essential. Changes in the machine’s magnetic influence should not be mistaken for changes in the surrounding subsurface conditions.

The Gouda UXO magnetometer module

The Gouda UXO magnetometer module is designed to minimise interference from the measurement assembly through its non-magnetic housing.

Its triaxial sensor measures the magnetic field in the X, Y and Z directions. The calculated resultant and gradient provide additional information to help specialists interpret changes in the surrounding magnetic field.

While the CPT rig provides the pushing force needed for intrusive investigations, it also forms part of the measurement environment.

Understanding and accounting for its magnetic influence is essential for reliable data interpretation and effective UXO detection.