Instruments

Geophysical instruments are designed to measure physical properties of the ground, water, or structures to reveal subsurface conditions without excavation. Each instrument type corresponds to a specific physical principle—electromagnetic fields, seismic waves, electrical resistivity, gravity, or magnetic response.
This page provides a clear overview of the most commonly used instruments in near-surface and applied geophysics.

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Ground-Penetrating Radar (GPR)

What it measures:
High-frequency electromagnetic reflections generated by contrasts in dielectric permittivity.

Typical uses:

• Utility locating (pipes, cables)

• Concrete scanning and structural assessment

• Archaeology and cultural heritage

• Road, bridge, and airport pavement evaluation

• Void and cavity detection

Key advantages:
High resolution, fast data collection, minimal site disturbance.

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Seismographs (Seismic Data Acquisition Systems)

What they measure:
Ground vibration and elastic wave propagation caused by natural or artificial sources.

Typical uses:

• Depth to bedrock

• Rippability assessments

• Subsurface layering and velocity profiling

• Geotechnical investigations

• Infrastructure and foundation studies

Key advantages:
Robust method for characterizing stiffness, stratigraphy, and mechanical properties.

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Geoelectrical Instruments (ERT – Electrical Resistivity Tomography)

What they measure:
Resistivity distribution using electrodes that inject current and record potential differences.

Typical uses:

• Groundwater exploration

• Contaminant mapping

• Depth to bedrock

• Landslide and geological hazard investigations

• Archaeological mapping

Key advantages:
Excellent for imaging moisture variations, lithology changes, and subsurface structures.

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Electromagnetic (EM) Instruments

What they measure:
Induced electromagnetic fields and ground conductivity.

Typical uses:

• Soil conductivity mapping

• Locating buried metal objects

• Environmental assessments

• Agricultural soil evaluation

• UXO reconnaissance

Key advantages:
Fast, no galvanic contact required, often used for large-area mapping.

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Marine Geophysical Instruments

What they measure:
Acoustic, electric, magnetic, or EM properties beneath water bodies.

Typical uses:

• Bathymetry and sub-bottom profiling

• Sediment characterization

• Pipeline and cable route assessment

• Harbor, coastal, and offshore engineering

Key advantages:
Essential for underwater infrastructure and marine research.

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Metal Detectors

What they measure:
Electromagnetic response of metallic objects.

Typical uses:

• Archaeological surveys

• UXO and target detection

• Security sweeps

• Locating buried infrastructure

Key advantages:
Simple, fast, effective for shallow metallic targets.

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Gravimeters

What they measure:
Minute variations in Earth’s gravitational field.

Typical uses:

• Detecting density contrasts

• Karst and cavity studies

• Mineral exploration

• Geotechnical and engineering geology

Key advantages:
Highly sensitive, offers insight into large-scale density distribution.

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XRF Analyzers (X-Ray Fluorescence)

What they measure:
Elemental composition of materials through X-ray fluorescence.

Typical uses:

• Geochemical screening

• Soil contamination analysis

• Mineral identification

• Archaeological material characterization

Key advantages:
Portable, non-destructive, immediate elemental results.

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Instrument Selection Guide

Use this quick reference to select the right instrument for a task: