Glossary
Term  Description 

Amplitude preservation frequency 
The NyquistShannon theorem ensures that the spectral content
of the original signal is preserved.
If the amplitude of the signal peak is to be preserved, a higher
minimal sampling rate is required. Maximum amplitudes values are often
used for further analysis.
`f_(Ampl)=f*12` 
Bandwidth  Frequency range of the transmitted GPR signal measured at a decay of 3 dB below the maximum value. 
Crossline 
Distance between profiles. Other terms:

Depth estimation 
Predicting the depth that can be reached with a GPR system
is very difficult.The formulas do not account for the frequency
dependency. The maximum depth can be calculated: `z = 35/sigma` Another way to calculate the exploration depth is:`z = (15.9*sqrt(epsilon_r))/sigma` Both formulas are valid for a signal attenuation α > 0.1 dB/m and a conductivity σ > 1 mS/m.In most circumstances both values are too high when compared with the effective penetration depth on site. 
Dielectric constant 
`epsilon_r` Other terms:

Footprint 
Theoretical model to estimate the area covered by the antenna
at a specific depth, length A is perpendicular,
length B is parallel to the antenna:
`A = lambda/4 + z/(sqrt(epsilon_r1))` `B = A/2` 
Fresnelzone 
Measure for the horizontal resolution (1/4 of the wavelength)
of the signal (so called first fresnelzone) that can be achieved
with a given antenna frequency and in a specified material:
`r = sqrt((lambda z) / 2 + lambda^2/16)` 
Frequency  The centre frequency f of the antenna is normally specified in MHz. For standard GPR antennas the bandwidth of the antenna is approximately equal to the centre frequency. 
Inline 
Distance between two consecutive traces along the measurement line. Other terms:

Loss tangent 
The loss tangent is the ratio of the total energy loss to
the total energy storage.
`tan delta=(17.8*sigma) / (epsilon_r*f)` 
Measurement conditions 
Determination of the central frequency of an antenna
is very much depending on the coupling. Hence it is important
to know in wich material the specified antenna frequency was
determined. If the frequencies are determined in air the actual frequency content of the data can be up to 20 % higher compared to normal ground conditions. 
Nyquist frequency 
The Nyquist frequency is the maximum recordable frequency
that can be recorded at a given sampling rate. All higher
frequencies are aliased.
`f_(Nyquist)=1/(2*delta t)` 
Offset  Distance between transmitter and receiver of an antenna (TxRx distance). This value is necessary for different advanced processing steps like NMO. 
Parallel broadside 
Survey configuration with a transmitter (Tx) and receiver (Rx)
antenna parallel to each other with their main radiation direction
perpendicular to the survey direction. Other terms:

Penetration depth  This is another, more sophisticated estimate of the maximum depth of the system. For a groundcoupled antenna and a point reflector the frequency dependent signal decay (S) with depth for the material is estimated (see graph). The detection limit for a conventional normal system is indicated by (dN) and the one for a modern high performance, lownoise system by (dH). The intersections on the graph give an estimate of the maximum depth. 
Perpendicular broadside 
Normal survey configuration with a transmitter (Tx) and receiver (Rx)
antenna parallel to each other with their main radiation direction
parallel to the survey direction. Other terms:

Profile 
Display of consecutive traces measured along a continuous survey path. Other terms:

QEstimation 
Change of the shape of the radar pulse as it propagates
through the material. This is an effect of freuqency
dependant attenuation of electromagnetic waves. This effect is
almost linear with frequency:
`Q=(sigma)/(2*pi*f)+1` 
Range  Length of the recording window, specified in nanoseconds. 
Required sampling interval 
According to Textronix 10 samples per cycle are required.
The highest frequency value can be approximated by double
the antenna frequency. Hence the required sampling interval
can be estimated by:
`deltat_(required) = 100000/(2*f)` 
Required spatial accuracy 
If full 3D GPR data shall be recorded the accuracy with which
the position should be maintained and recorded is:
`deltax = 5/f` 
Required spatial interval 
If full 3D GPR data shall be recorded a minimum spatial sampling
interval (horizontal distance between traces) is required:
`Deltax = lambda/4` 
RTS 
Abbreviation for realtime sampling.
The advances in electronics permit
recording of much more than a single sample per transmitted pulse.
The gain in speed is significant and is used for stacking of the
data, resulting in a significant higher S/N ratio. Together with
a modified recording system the bandwidth of the signal is enlarged
at the same time. RTS might be called differently by each manufacturer. Other terms:

Sample 
Individual eletrical value recorded in the system. Other terms:

Sampling interval 
`deltat` 
SFCW 
Abbreviation for steppedfrequency continuous wave. Other terms:

Signal attenuation 
Reduction of the signal amplitude by the material:
`alpha = 1.69*(sigma/sqrt(epsilon_r))` 
Speed of light  c = 0.3 m/ns 
Time or Depthslice 
Other terms:

Trace 
Recording of individual samples at a single point representing
the variation of the returned signal with time. Other terms:

Velocity 
Propagation speed of the electromagnetic wave for nonmagnetic
materials in the ground:
`v = c / sqrt(epsilon_r)` 
Wavelength 
Distance between three consecutive zerocrossing of the wave,
measured in the material to be investigated:
`lambda = c / (f*sqrt(epsilon_r))` 
Many of the provided formulas are simplified alghorithms for complex and frequency dependent variables. Nevertheless the formulas give realistic estimations.
References:
A.P. Annan: Ground Penetrating Radar. Principles: Workshop Notes, Sensors & Software Inc., 1992
A.P. Annan: Ground Penetrating Radar. Principles, Procedures and Applications, Sensors & Software Inc., 2003
A.P. Annan, S.W. Cosway: Simplified GPR Beam Model for Survey Design, Extended abstract of 62nd Annual International Meeting of the Society of Exploration Geophysicists, New Orleans, 1992
L.B. Conyers: GroundPenetrating Radar for Archaeology, Alta Mira Press, Walnut Creek, 2004
J.D. Daniels: Ground Penetrating Radar, IEE, London 2004
M. Dossi, E. Forte, M. Pipan: Minimum threshold for the sampling rate to prevent amplitude distortions in aliasingfree GPR surveys. 17th International Conference on Ground Penetrating Radar (GPR), 2018
M. Grasmueck, R. Weger, H. Horstmeyer: Fullresolution 3D GPR Imaging, Geophysics 70,1, K12K19, 2005
O. Yilmaz: Seismic Data Processing. Investigations in Geophysics, SEG, Tulsa, 1987