CMPAnalysis-methods: Velocity Analysis of CMP Gather

In emanuelhuber/RGPR: Ground-penetrating radar (GPR) data visualisation, processing and delineation

Velocity Analysis of CMP Gather

Description

Transform the space-time domain of the radargram into a velocity-time domain to obtain the velocity spectrum (i.e. change in wave velocity with depth or time). This is achieved by applying Normal Move-Out (NMO) corrections to the radargram for the range of selected velocities and computing a coherency measure for each result. In RGPR, the coherency measure can be defined using different functions: "semblance", "winsemblance", "wincoherence", "wincoherence2".

Usage

## S4 method for signature 'GPR'
CMPAnalysis(
  x,
  method = c("semblance", "winsemblance", "wincoherence", "wincoherence2"),
  v = NULL,
  w = NULL
)

Arguments

x	An object of the class GPR
method	A length-one character vector
v	A numeric vector defining at which velocities the analysis is performed
w	A length-one numeric vector defining the window length for the methods 'wincoherence' and 'wincoherence2'.

Details

either use 'rec' and 'trans' to compute the distance between the antennas or give the distance between the antennas (asep) or seq(x@antsep, by = x@dx, length.out = length(x))

semblance

also described as the ratio of input to output energy (Niedell and Taner, 1971)

winsemblance

windowed semblance

wincoherence

Windowed coherence measure based on eigen-decomposition that estimates the signal-to-noise ratio for high resolution velocity analysis (Sacchi, 2002)

wincoherence2

Windowed coherence measure based on a log-generalized likelihood ratio which tests the hypothesis of equality of eigenvalues (Key and Smithson, 1990)

References

• Neidell and Taner (1971) Semblance and other coherency measures for multichannel data. Geophysics, 36(3):482-497.

• Key and Smithson (1990) New approach to seismic-reflection event detection and velocity determination. Geophysics, 55(8):1057-1069.

• Textbook: Sacchi (2002) Statistical and Transform Methods in Geophysical Signal Processing

emanuelhuber/RGPR documentation built on March 18, 2024, 8 p.m.