Ground penetrating radar

Ground-penetrating radar (GPR): non-destructive investigation of the subsurface

Ground-penetrating radar (GPR) reveals what lies hidden in the ground, within structures and beneath road surfaces – non-destructively. Our range includes GPR technology for utility location, structural diagnostics and subsurface investigation. The following overview explains how it works and helps you select the appropriate antenna frequency.

How does GPR work?

GPR transmits short electromagnetic pulses into the ground. Differences in dielectric properties – that is, changes in material within the subsurface – reflect the signals back. The transit time and amplitude of the reflections are used to generate profiles in which objects and layer boundaries can be made visible.

Antenna frequencies & application profiles

The selected antenna frequency determines the balance between penetration depth and resolution:

• ~200–250 MHz: great penetration depth (in suitable soils), lower resolution – ideal for utility routes and larger objects.
• ~400 MHz: a good compromise for utility location and depths down to the metre range.
• ~700–900 MHz: high detail resolution for dense networks, concrete and close-range applications.
• ≥1.2 GHz: very high resolution for shallow features and structural diagnostics.

Soil conditions

Dry, sandy and rocky soils allow for good penetration depth. High conductivity – for example, due to wet clay or saline soil – strongly attenuates the signal, however. The depth that can actually be achieved therefore depends largely on the subsurface.

Typical applications

• Utility and route location (power, communications, pipelines)
• Layer thicknesses, backfills, voids and undermining
• Concrete testing (reinforcement/cover) and road surface investigation
• 3D data sets for as-built modelling and documentation

Selection guide: finding the right GPR

• Target size: small objects require a higher frequency; great depth requires a lower frequency.
• Subsurface: take soil conductivity and moisture into account.
• Output format: quick 2D profiles versus 3D volumes from a dense grid.
• Handling: hand-held unit, cart or vehicle-mounted carrier – depending on the area and pace.

Frequently asked questions about ground-penetrating radar (GPR)

How deep does GPR “see”?

This depends on the frequency and the soil: from decimetres (high frequency) up to several metres (low frequency, in favourable soil conditions).

Does GPR replace utility location using a transmitter/receiver?

GPR complements traditional location – particularly for non-metallic objects or when the position is unknown. Often, a combination of both methods is the most reliable.

Can I output exact depths?

Yes, with appropriate calibration of the propagation velocity. Without calibration, the depth readings are relative in nature.

Does GPR work in the rain?

Wet, clayey soil strongly attenuates the signal. In unfavourable conditions, you should adjust the frequency and setup or consider alternatives.