Glossary

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Antenna Separation
Spacing between transmitting and receiving antennas.
Attenuation
A measure in the reduction of signal strength as it progresses through a loss medium during transmission. This loss can be due to a spread as the wave expands out into the medium, or due to an ohm loss resulting from the finite conductivity of the medium. Attenuation is the opposite of amplification, and is normal when a signal is sent from one point to another.
Bandwidth
The range of frequencies or wavelengths over which a given device transmits or detects signals above a specified amplitude or power. The amount of data transmitted in a fixed amount of time is expressed in cycles per second, or Hertz (Hz).
Clutter
Unwanted reflections from the ground, from within the ground, or from above the ground. In the case of ground penetrating radar (GPR), clutter can be produced by boulders, soil interfaces and other sources of interference that are not of interest.
CMP
Common Mid-Point is the point halfway between the source and receiver (in a survey where transmitter and receiver antenna separations are changed, but the mid-point remains constant). It is above the common depth point, or common reflection point.
Control Unit
An electronic instrument that directs the operation of other units (recorders, processors, displays, survey wheels, power supplies, etc.) by providing timing and control signals. It reads and interprets instructions to determine the sequence for processing data. It also allows radar functions such as range, gain and filtering to be adjusted. A C/U can be analog, digital, or hybrid.
COR
Common Offset Reflection is a technique for obtaining one-fold reflection data (in a survey type where a constant antenna separation is maintained).
Cross Section
An image that results from a side-by-side display of a number of traces from adjacent spatial measurement positions, which shows the intersection of a figure in a two-dimensional space with a line, or of a body in a three-dimensional space with a plane.
Depth of Penetration
A measure of how deep a radar wave can penetrate into a material. At radar frequencies in conductive material (sea water, metallic materials, clay soils, etc.) the rate of attenuation is very great and the wave may penetrate only a short distance (<1m) before being reduced to a negligibly small value. In a resistive dielectric earth material (fresh water, granite, quartz sand, etc.), where the losses are low, the depth of penetration can be quite great (>30m).
Echoes
Radar energy reflected from a given target or object back to its point of origin.
Electromagnetic Radiation
A form of energy emitted and absorbed by charged particles that exhibits wave-like behavior as it travels through space. EMR has both electric and magnetic field components that, in phase with each other, oscillate at right angles to each other and to the direction of propagation.
Geophysical Investigation
The use of multiple survey techniques in a cost-efficient manner to gain maximum information on the physical properties of sub-surface structures.
Ground Penetrating Radar
A system that uses radar pulses to image a 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, pavement and structures. It can detect objects, changes in material, and voids and cracks. GPR systems have wide applications, such as locating underground utility lines, monitoring airplane runways for structural integrity, detecting unexploded land mines, conducting groundwater studies, collecting forensic research, and surveying land for construction purposes.
Nodig or No-dig
A system that uses radar pulses to image a 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, pavement and structures. It can detect objects, changes in material, and voids and cracks. GPR systems have wide applications, such as locating underground utility lines, monitoring airplane runways for structural integrity, detecting unexploded land mines, conducting groundwater studies, collecting forensic research, and surveying land for construction purposes.
Non-Destructive Testing
A wide group of analysis techniques used in science and industry to evaluate the properties of a material, component, or system without causing damage to the outer shell or surface. Because it does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting and research.
Reflection
The change in direction of radio waves at an interface between two different media, so that the wavefront returns into the medium from which it originated.
Resolution
Refers to the sharpness and clarity of an image, and the ability to separate two features that are very close together. The minimum separation of two bodies before their individual identities are determined is impossible to interpret.
Scatter
The loss of signal caused by the irregular and diffuse dispersion of energy resulting from microscopic variations or impurities in the transmission medium.
Station Interval
The spatial distance between observation points along a survey traverse line or mesh points on a grid.
Scatter
The loss of signal caused by the irregular and diffuse dispersion of energy resulting from microscopic variations or impurities in the transmission medium.
Transducer
A device that is actuated by energy from one system that supplies energy (usually in another form) to a second system. It is the name commonly used when the GPR antenna, electronics and shield are combined into one physical unit.
Transmitter
An electronic device that, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.
Vertical Resolution
The ability to separate two features within one scan that are very close together. The minimum separation of two bodies before their individual identities are determined is lost on the resultant map or cross-section. It is a function of transducer frequency, sampling interval and range.