NAME
SPECAL - module to perform SPECtral AnaLysis on seismic
data.
SYNOPSIS
SPECAL [ Command Line Arguments Required. ]
DESCRIPTION
SPECAL computes and displays either one dimensional (1D) or
two dimensional(2D) spectral analysis on seismic data. In
the 1D mode, up to 50 traces may be analyzed concurrently,
with "movie loop", sequential, or random access of the
amplitude spectra or the phase spectra. The user may choose
between linear scaling or log scaling on the 1D amplitude
displays. In the 2D mode, up to 1024 traces may be
analyzed.
The displays for the 1D spectra are black and white only,
with fully anotated frequency and (normalized) amplitude
scales. [Note that normalization of the amplitude spectra
are on a per-trace basis only. That is, the program does
not normalize all concurrent spectra with the same normali-
zation constant.] The record and trace number of the spec-
trum being displayed is annotated at the bottom of the
display, so that you always know which spectrum you are
looking at.
The display for the 2D spectra is a color contour only, with
fully annotated spatial and temporal frequency scales. Up
to ten 2D spectra may be computed and displayed (simultane-
ously, if desired) during a specal session. There is a
ColorEditor function which allows the user to edit the
colormap. As of this release, all 2D spectra use the same
colormap; i.e., any change to a colormap from any one of the
2D displays will be reflected in all the 2D displays.
Usage Notes
Menu bar
To use SPECAL, ensure that you have the appropriate USP
libraries in your path and enter the command specal. A menu
bar will appear in the upper left portion of your screen.
On the menu bar are two buttons. From the left, the first
button is the file (and program exit) button. Selecting the
file button causes a second menu to appear, permitting input
file (SelectFile) selection, or exit from the program.
Select the SelectFile option first to get a selectable list-
ing of the files in your working directory. When the
appropriate file is selected, the menu disappears, and the
parameter selection menu appears, with established defaults
for all parameters. These defaults come from the line
header information in the selected file. You can enter the
desired record and trace numbers and window parameters for
analysis as well as select 1D or 2D spectral computation.
Move down the parameter list by "clicking" in the desired
parameter box, or tabbing. Once all parameters are entered
(or the supplied defaults taken), select the "ok" button to
begin analysis computation. When the analysis computation
is completed, the results of the analysis are automatically
displayed.
The second button is labeled Display. It allows you to
bring up the parameter menu again to select different
options for the same input file. It also allows you to
redisplay any of the displays previously created. NOTE:
Only one 1D amplitude display (or set of traces) is saved --
that means only linear scaling OR log scaling, not both.
The last one created is the one available, as well as for
the phase option. For 2D, up to 10 different spectra may be
computed, and then recalled for display (all at once if
desired!). The 2D redisplay button brings up a list of
spectra created, and you may select the desired one by
clicking on it.
On the parameter menu panel, a new option has been added:
PreviousSettings. This option allows you to bring up the
parameter settings last used, in case you are processing
multiple datasets (different filenames), but want to use the
same parameters, without having to type them in for each
dataset.
NOTE: This release allows the sample to be in milleseconds
or microseconds. If the value of SmpInt in the line header
is greater than 32, microseconds is assumed. On the parame-
ters menu panel for Offset from Start of Window(phase only),
Window Start Time, and Window End Time will be expressed in
the same units as the input sample interval.
1D Spectra Display
When the 1D option is selected, the amplitude spectra
display panel appears. Across the top of this panel is a
control panel containing three additional buttons. Use the
Dismiss button to "unshow" this panel. Use the Select Data
button to randomly select the specta for display from a list
of the traces analyzed. Use the Animate button to bring up
an additional control panel for "movie loop" or sequential
access of the spectra. The phase spectrum display has the
same options as the amplitude spectra display
2D Spectrum Display
When the 2D option is selected the 2D amplitude spectrum
display panel appears. Across the top of this panel is a
control panel containing three buttons. Use the Dismiss
button to "unshow" this panel. Use the ChangeColorScale
button to edit the colormap. Use the Zoom button to bring
up the menu to specify the zoom dimensions, or to dismiss
the zoomed panel. When zooming, after the dimensions are
specified and you click on OK, then define the box to be
zoomed by using the left mouse button to locate the starting
point, and then drag the box to the desired size. The size
of the 2D spectra panel is established by the program
according to the number of temporal and spatial samples
selected and may not be changed by the user. Each 2D panel
may be individually iconified, and the icon is identified by
the window number.
AUTHOR
Richard Crider ES&S Houston (Design and protyping)
Marilyn Miller APR Tulsa (MOTIF implementaton)
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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