SUMMARY

Calculate a spectrogram equal to the difference between two smoothed versions of the same spectrogram.

SYNTAX

SCALLOP options

where options are one or more of the following:

WINDOW v
SLICE v
ORDER n
CBAR    {ON|OFF}
YMIN v
YMAX v
FMIN v
FMAX v
BINARY|FULL
METHOD {PDS|MEM|MLM}
{COLOR|GRAY}
PRINT {pname}

INPUT

WINDOW v:	Set the sliding data window length in seconds to v. This window length determines the size of the fft.
SLICE v:	Set the data slice interval in seconds to v. A single spectrogram line is produced for each slice interval.
ORDER n:	Specifies the number of points in the autocorrelation function used to compute the spectral estimate.
CBAR {ON|OFF}:	Turn reference color bar on or off.
BINARY|FULL:	Produce a binary image, or a full color image.
YMIN v:	Specifies the minimum frequency to plot.
YMAX v:	Specifies the maximum frequency to plot.
FMIN v:	Specifies the smallest bandwidth over which each slice in the spectrogram will be smoothed.
FMAX v:	Specifies the maximum bandwidth over which each slice in the spectrogram will be smoothed.
METHOD {PDS|MEM|MLM}:
	Specifies the type of spectral estimator used. MLM stands for maximum likelihood and MEM stands for maximum entropy spectral estimators, respectively. See description and references below.
{COLOR|GRAY}:	Specifies a color or grayscale image.
PRINT {pname}:	Prints the resulting plot to the printer named in pname, or to the default printer if pname is not used. (This makes use of the SGF capability.)

DEFAULT VALUES

SCALLOP WINDOW 2 SLICE 1 METHOD MEM ORDER 100 YMIN 0 YMAX FNYQUIST FMIN 2.0
    fmax 6.0 full color

DESCRIPTION

The scalloping command computes a spectrogram equal to the difference between two smoothed version of the same spectrogram. Depending on the choice of smoothing parameters, fmin and fmax, the resulting spectrogram can enhance small amplitude spectral features that are more difficult to observe in a conventional spectrogram. This is particularly useful when looking for features like high frequency spectral modulations in seismic signals from mine blasts (c.f., Hedlin, 1990, Wuster, 1993).

LIMITATIONS

The size of the image in the frequency direction is 512.

PROBLEMS

There is currently very little error checking of the headers to make sure that they are from the same component and are contiguous in time. This will be corrected in the future.

HEADER VARIABLES

REQUIRED:	DELTA
CHANGED:	NPTS, DELTA, B, E, IFTYPE, DEPMIN, DEPMAX, DEPMEN
CREATED:	NXSIZE, XMINIMUM, XMAXIMUM, ,BREAK NYSIZE, YMINIMUM, YMAXIMUM

LATEST REVISION

May 26, 1995 (Version 00.31)