Ground-penetrating radar


Ground-penetrating radar

Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This non-destructive method uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can be used in a variety of media, including rock, soil, ice, fresh water, pavements and structures. It can detect objects, changes in material, and voids and cracks.

GPR uses transmitting and receiving antennas. The transmitting antenna radiates short pulses of the high-frequency (usually polarized) radio waves into the ground. When the wave hits a buried object or a boundary with different dielectric constants, the receiving antenna records variations in the reflected return signal. The principles involved are similar to reflection seismology, except that electromagnetic energy is used instead of acoustic energy, and reflections appear at boundaries with different dielectric constants instead of acoustic impedances.

The depth range of GPR is limited by the electrical conductivity of the ground, and the transmitting frequency. As conductivity increases, the penetration depth also decreases. This is because the electromagnetic energy is more quickly dissipated into heat, causing a loss in signal strength at depth. Higher frequencies do not penetrate as far as lower frequencies, but give better resolution. Optimal depth penetration is achieved in dry sandy soils or massive dry materials such as granite, limestone, and concrete where the depth of penetration could be up to 15 m. In moist and/or clay laden soils and soils with high electrical conductivity, penetration is sometimes only a few centimetres.

Ground-penetrating radar antennas are generally in contact with the ground for the strongest signal strength; however, GPR horn antennas can be used 0.3 to 0.6 m above the ground.

Applications

GPR has many applications in a number of fields. In the Earth sciences it is used to study bedrock, soils, groundwater, and ice. Engineering applications include Nondestructive testing (NDT) of structures and pavements, locating buried structures and utility lines, and studying soils and bedrock. In environmental remediation, it is used to define landfills, contaminant plumes, and other remediation sites. In archaeology it is used for mapping archaeological features and cemeteries. It is used in law enforcement for locating clandestine graves and buried evidence. Military uses include detection of mines, unexploded ordnance, and tunnels.

Before 1987 Frankley Reservoir in the UK was leaking 540 litres per second. In that year Ground-penetrating radar was used successfully to isolate the leaks. [Penguin Dictionary of Civil Engineering p347 ("Radar")]

Three-dimensional imaging

Individual lines of GPR data represent a sectional (profile) view of the subsurface. Multiple lines of data systematically collected over an area may be used to construct three-dimensional or tomographic images. Data may be presented as three-dimensional blocks, or as horizontal or vertical slices. Horizontal slices (known as "depth slices" or "time slices") are essentially planview maps isolating specific depths. Time-slicing has become standard practice in archaeological applications, because horizontal patterning is often the most important indicator of cultural activities.

Limitations

The most significant performance limitation of GPR is poor performance in high-conductivity materials such as clayey soils. Performance is also limited by signal scattering in heterogeneous conditions (e.g. rocky soils).

Other disadvantages of currently available GPR systems include:
*Interpretation of radargrams is generally non-intuitive.
*Considerable expertise is necessary to effectively design, conduct, and interpret GPR surveys.
*The cost of GPR equipment and software is relatively high.
*Relatively high energy consumption can necessitate large cumbersome batteries for extensive surveys.Recent advances in GPR hardware and software have done much to ameliorate these disadvantages, and further improvement can be expected with ongoing development.

Frequency regulation

In 2005, the European Telecommunications Standards Institute deemed it necessary to regulate GPR equipment and GPR operators to control excess emissions of electromagnetic radiation. The European GPR association (EuroGPR) was formed as a trade association to represent and protect the legitimate use of GPR in Europe.

imilar technologies

Wall-penetrating radar can read through walls and even act as a motion sensor for police.

The "Mineseeker Project" seeks to design a system to determine whether landmines are present in areas using ultra wideband synthetic aperture radar units mounted on blimps.

References

External links

* [http://www.eurogpr.org EUROGPR – The European GPR regulatory body]
* [http://www.gprmax.org GprMax – GPR numerical simulator based on the FDTD method]


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Ground Penetrating Radar — Ein Bodenradar, auch Georadar, engl. Ground Penetrating Radar (GPR) oder Radio Echo Sounding (RES), misst Störungen in den oberen Schichten des Erdbodens durch Reflexion elektromagnetischer Strahlung. In der Geophysik dient es zur Untersuchung… …   Deutsch Wikipedia

  • ground penetrating radar — noun a device which uses radio waves that penetrate the ground to produce images of structures beneath the ground; used particularly in archaeology. Abbrev.: GPR …   Australian English dictionary

  • Radar MASINT — is one of the subdisciplines of Measurement and Signature Intelligence (MASINT) and refers to intelligence gathering activities that bring together disparate elements that do not fit within the definitions of Signals Intelligence (SIGINT),… …   Wikipedia

  • Radar astronomy — is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the echoes. This research has been conducted for four decades. Radar astronomy differs from radio astronomy in that the latter is a… …   Wikipedia

  • Radar de apertura sintética — Saltar a navegación, búsqueda Imagen de la superficie de Venus cartografiada por el SAR de la sonda Magallanes Un Radar de Apertura Sintética (acrónimo SAR, del inglés Synthetic Aperture Radar) es un tipo de sistema radar. C …   Wikipedia Español

  • Radar — For other uses, see Radar (disambiguation). A long range radar antenna, known as ALTAIR, used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on Kwajalein Atoll …   Wikipedia

  • Radar à pénétration de sol — Pour les articles homonymes, voir RPS et GPR. Diagramme montrant les données d un sondage par radar à pénétration de sol dans un cimetière historique en Alabama, États Unis. Les réflections …   Wikipédia en Français

  • radar — /ray dahr/, n. 1. Electronics. a device for determining the presence and location of an object by measuring the time for the echo of a radio wave to return from it and the direction from which it returns. 2. a means or sense of awareness or… …   Universalium

  • ground-proximity warning system — A system that warns the crew if the aircraft’s current flight path would result in impact with the ground. The system automatically and continuously monitors the aircraft’s flight path with respect to the terrain at all altitudes between 50 and… …   Aviation dictionary

  • History of radar — The history of radar starts with experiments by Heinrich Hertz in the late 19th century that showed that radio waves were reflected by metallic objects. This possibility was suggested in James Clerk Maxwell s seminal work on electromagnetism.… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.