Groundnut oil

Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This nondestructive 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 have applications in a variety of fields, 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.

History

The concept of GPR has been in existence since the early 20th century. However, it was not until the 1970s that the technology became a practical tool for field work. The development of GPR was largely driven by the need for a non-invasive method to locate and map subsurface features.

Principles

GPR uses a high-frequency radio wave and transmits it into the ground. When the wave hits a buried object or a boundary with different dielectric constants, the receiving antenna records 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.

Applications

GPR has many applications. It is used in geology, archaeology, environmental science, military, and law enforcement. In geology, it is used to study bedrock, soils, groundwater, and ice. It is used in environmental science to study wetlands, peatlands, and coastal sediments. In archaeology, it is used to detect and map subsurface archaeological artifacts, features, and patterning.

Limitations

While GPR provides many advantages, it also has limitations. The depth range of GPR is limited by the electrical conductivity of the ground, the transmitted center frequency and the radiated power. As conductivity increases, the penetration depth decreases. This is because the electromagnetic energy is more quickly absorbed into the ground.

See also

• Seismology
• Radar
• Archaeology
• Geology