| Symbol or Term |
Explanation |
| α |
exponential attenuation coefficient – normal units dB/m (see attenuation) |
| k |
relative permittivity or dielectric constant |
| σ |
electrical conductivity – normal units mS/m |
| v |
propagation velocity – normal units m/ns |
| dB/m |
decibels/metre, common unit for attenuation,α |
| m/ns |
metre/nanosecond, common unit of GPR velocity, v (see nanosecond) |
| mS/m |
milli Siemens/met re, common unit for conductivity,σ |
| ns |
nanosecond, normal unit of GPR time (see nanosecond) |
| ps |
picosecond = 0.001 ns =10-12s, occasion unit of GPR time |
| μs |
microsecond = 1000ns =10-6s, occasion unit of GPR time |
| COR |
Common Offset Reflection (survey type where a constant antenna separation is maintained). |
| CMP |
Common Mid-Point (survey type where a transmitter and receiver antenna separation are changed but the mid point remains constant) |
| GPR |
Ground Penetrating Radar |
| EM |
Electromagnetic (common abbreviation) |
| antenna |
Device used to couple electromagnetic energy into the ground. Sometimes called a transducer. |
antenna
separation |
Spacing between transmitting and receiving antennas. |
| attenuation |
A reduction in signal amplitude caused by energy dissipation in the transmitt ing media (see α) |
| bandwidth |
The range of frequencies over which a given device transmits or detects signals above a specified amplitude or power |
centre
frequency |
Middle of the frequency band defined by a device's bandwidth |
| conductivity |
The ability of a material to conduct electrical current. In isotropic materials the reciprocal of resistivity. Sometimes called specific conductance. Units are siemen/m or S/m. (Or occasionally, mhos/m). For GPR, usually expressed as mS/m. Common symbol σ |
| nanosecond |
10-9s (One Billionth of a second) |
| radio wave |
Electromagnetic fields that travel through a material as waves and typically have oscillating frequencies in the 1 GHz to 10 GHz range |
| receiver (Rx) |
General term for electronics devices used to detect fields and translate signals into records or displays |
| resolution |
The minimum separation of two objects before their individual responses merge into a single response |
signal
amplitude |
A measure of the strength of the radio wave signal |
station
interval |
Spatial distance between observation points along a survey traverse line or mesh points on a grid |
| step size |
See station interval |
| transmitter (Tx) |
General term used for electronics devices used to create propagating electromagnetic fields |
| transducer |
Name used where GPR antenna, electronics, and shield are combined into one physical unit |
sample
point |
Signal amplitude measured at specific point in time |
| trace |
Sequence of sample points from a single GPR channel that indicate time variation of signal amplitude |
| cross-section |
Image that results from side-by-side display of a number of traces which are from adjacent spatial measurement position |
| gain |
Process of amplifying signals to match recording device or display dy namic range |