estimateTime0: Estimate and set time-zero

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

Estimate and set time-zero

Description

estimateTime0 estimates for each trace individually the first wave break, computes the corresponding time-zero knowing the propagation speed of the electromagnetic wave through air and returns an object of the class GPR with updated time-zero. It is possible to apply a function provided by the user (e.g., FUN) on time-zero (e.g., to set time-zero equal to the average value of the time-zeros computed for every traces; in this case, all traces would have the same time-zero).

Usage

## S4 method for signature 'GPR'
estimateTime0(
  x,
  method = c("coppens", "threshold", "MER"),
  thr = NULL,
  w = NULL,
  ns = NULL,
  bet = NULL,
  shorten = TRUE,
  c0 = 0.299,
  FUN = NULL,
  ...,
  track = TRUE
)

Arguments

x	[GPR class] An object of the class GPR
method	[character(1)] Method to be applied (either coppens, threshold or MER). "coppens" corresponds to the modified Coppens method, "threshold" to the threshold method, and "MER" to the modified energy ratio method.
thr	[numeric(1)] Threshold for the signal amplitude (in %) at which time zero is picked (only for the threshold method). thr ranges between 0 and 1.
w	[numeric(1)] Length of the leading window in unit of time (only for the modified Coppens and modified energy ratio methods). Recommended value: about one period of the first-arrival waveform.
ns	[numeric(1)] Length of the edge preserving smoothing window in unit of time (only for the modified Coppens method). Recommended value: between one and two signal periods. When ns = NULL the value of ns is set to 1.5 * w.
bet	[numeric(1)] Stabilisation constant (only for the modified Coppens method). Not critical. When bet = NULL the value of bet is set to 20% of the maximal signal amplitude.
shorten	[logical(1)] If TRUE, each trace is shortened by removing the samples that are 2 \times w after the maximum value (only for method = "coppens" or method = "MER"). You may set shorten = FALSE if the first wave break occurs after the maximum absolute amplitude time.
c0	[numeric(1)] Propagation speed of the GPR wave through air in unit of space per unit of time (generally in m/ns).
FUN	[function] A function to apply on the estimated time-zero of every traces (e.g., mean or median to get set a single time-zero value to the data).
...	[ANY] Further arguments to be passed to FUN.

Details

This function is a wrapper for the following commands

• tfb <- firstBreak(x, ...)

• t0 <- firstBreakToTime0(tfb, x)

• time0(x) <- t0 (if FUN is not NULL time0(x) <- FUN(t0, ...))

Modified slots

• time0: new estimated time-zero.

• proc: updated with function name and arguments.

Value

[GPR class] An object of the class GPR.

See Also

firstBreak to estimate the first wave break; firstBreakToTime0 to convert the first wave break into time zero. time0 and setTime0 to set time-zero; time0Cor to shift the traces such that they start at time-zero.

Examples

data("frenkeLine00")
x <- frenkeLine00
x1 <- estimateTime0(x, w = 10)
time0(x1)
x2 <- estimateTime0(x, w = 10, FUN = mean)
time0(x2)

emanuelhuber/RGPR documentation built on May 13, 2024, 9:31 p.m.