What is ground penetrating radar

Geophysical applications on environmental investigation, mineral prospecting, engineering, archaeology, forensics, hydrology...
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Resource
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What is ground penetrating radar

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A ground penetrating radar (GPR) is a radar. Unlike regular radars which transmit electromagnetic waves through air or free space to detect airplanes, ships or missiles, GPR is designed and used for transmitting electromagnetic waves into the ground for subsurface geological mapping or underground object detecting.

While the frequency range of radars can be from several Hz to several hundred GHz, the GPR frequency range is usually from about 10 MHz to a few GHz. In one hand, the GPR frequencies are kept high enough to differentiate subsurface materials with different dielectric properties, but not necessarily with different electrical conductivities or magnetic susceptibilities, making GPR unique in detecting some non-metallic objects such as artifacts, plastic explosives, PVC pipes and fiberglass tanks, etc. In the other hand, the GPR frequencies are kept lower enough for good penetration depths for its common applications.

While GPR is unique in underground object detecting compared to other detectors such as metal detectors and electromagnetic induction instruments, its main limitation is its penetration depth. The GPR penetration depth over electrically conductive materials such as clay soils is very limited and can be less than 1 foot, although it can easily reach tens of feet over favorable subsurface materials such as dry sands. Also, the higher the GPR frequency, the shallower the penetration depth.

There are a lot of GPR applications and it’s still growing. Below is just an incomplete application list:
--Archaeological mapping
--UXO/mine detection
--Mineral deposit delineation
--Geological mapping
--Pavement evaluation
--Bridge deck/concrete inspection
--Underground utility locating
--Underground storage tank locating
--Forensic investigation
--Treasure hunting

GPR are manufactured all over the world. Famous manufacturing companies include Geophysical Survey System, Inc. (GSSI), Mala Geoscience and Sensors & Software, etc. You can find more GPR manufactures on the list.

Trinder
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Re: What is ground penetrating radar

Post by Trinder »

Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. It is a non-intrusive method of surveying the sub-surface to investigate underground utilities such as concrete, asphalt, metals, pipes, cables or masonry.

This non-destructuve method uses electro magnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can have applications in a variety of media, including rock, soil, ice, fresh water, pavements and structures. In the right conditions, practitioners can use GPR to detect subsurface objects, changes in material properties, and voids and cracks.

GPR uses high-frequency (usually polarized) radio waves, usually in the range 10 MHz to 2.6 GHz. A GPR transmitter and antenna emits electromagnetic energy into the ground. When the energy encounters a buried object or a boundary between materials having different permittivities, it may be reflected or refracted or scattered back to the surface. A receiving antenna can then record the variations in the return signal. The principles involved are similar to seismology, except GPR methods implement electromagnetic energy rather than acoustic energy, and energy may be reflected at boundaries where subsurface electrical properties change rather than subsurface mechanical properties as is the case with seismic energy.

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