Ground-penetrating radar

Ground-penetrating radar (GPR) is a geophysical method that sends electromagnetic pulses into the ground and records reflections from subsurface boundaries and objects. Its results depend on contrasts in electrical properties, especially permittivity and conductivity.

Electromagnetic wave: A wave of oscillating electric and magnetic fields that carries energy through space or matter. GPR uses electromagnetic waves to probe below the surface.
Archaeological geophysics: The use of physical measurements to investigate buried archaeological remains without excavation. GPR maps buried walls, floors, graves, and other archaeological features.
Seismic reflection: A geophysical method that images subsurface structures from reflected elastic waves. It uses mechanical waves rather than GPR's electromagnetic pulses.
Wavelength: The distance between successive corresponding points on a wave, such as adjacent crests. Wavelength helps set the scale of structures that GPR can resolve.
GPR velocity analysis: The estimation of radar-wave velocity from GPR measurements to support depth conversion and interpretation. Uncertain velocity makes the depth of a GPR reflector uncertain.
Dielectric permittivity: A measure of how a material responds to an electric field and stores electrical energy. Permittivity contrasts change wave speed and produce reflections in GPR data.
Utility locating: The detection and mapping of buried pipes, cables, and other infrastructure. GPR can locate utilities where plans are incomplete or uncertain.
Electrical resistivity tomography: A method that reconstructs subsurface electrical resistivity from measurements at surface electrodes. It maps electrical properties directly, unlike GPR's interpretation of reflected pulses.
Frequency: The number of cycles of a periodic signal occurring per unit time. Higher antenna frequency generally improves detail but reduces penetration.
GPR migration: A processing technique that relocates reflected energy toward the subsurface structures that produced it. Migration can sharpen diffraction patterns but depends on an adequate velocity model.

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