Additional information on program TracePlot, Version 2.2

This document contains information on the correction of an error that was 
discovered in TracePlot, Version 2.1 (and 2.0) and also contains information on three
(3) enhancements to TracePlot, Version 2.0, which is not contained in the paper
documentation or in file Readme.Documentation.  Furthermore, the Version 2.2
disk contains one additional application which provides the means to change the
Macintosh "file-type" of a SEG-Y format file to one that TracePlot can recognize (if
necessary).

The error was that when reading a SEG-Y file that was written in 16- or 32-bit
integer format, Traceplot did not apply any scalar that might have been stored
in bytes 169-170 of the trace header.  In Version 2.2, this scalar is now properly
applied.

The enhancements are as follows:

Overlap Parameter:  In version 2.0, the explanation of this parameter for
GAIN=NORM, is correct and worked exactly as documented.  However, the
documentation for version 2.0 states that for GAIN=any number, overlap is the
maximum excursion to the left or right of 0 amplitude, in terms of trace
widths.  This feature did not work in version 2.0, and the parameter was
ignored.  In Versions 2.1 and 2.2, this feature works exactly as documented.

Trace Bias:  A parameter has been added which allows the user to specify a
"bias" for the variable area portion of the display.  Bias is defined as an
offset from the trace origin at which to begin plotting the variable area
portion of the trace.  The Bias is provided in terms of trace-width and can
vary from -1 to +1.

Example:  Default for bias is 0, which means that plotting of the variable area
portion of a trace begins at amplitude 0.  If the user provides a bias value of
.5, the plotting of the variable area portion of a trace will begin at 1/2 the
distance between the center of the trace being plotted and the center of the
trace immediately to its right.  Thus trace amplitudes which do not extend at
least half the distance to the next trace center to the right, will be plotted
as Wiggles (or not plotted at all if the plot style is Variable-Area only).

The main effect of the above example would be to decrease the amount of the
"filled-in", or variable area, portion of the plot, thereby making coherent
reflectors appear thinner, and more like a line-drawing, especially if the plot
style selected is Variable-Area only.  Conversely, a negative value for bias
will increase the amount of the variable area portion of the plot.

Trace Annotation Increment:  A parameter has been added which allows the user
to specify the trace annotation increment.  In version 2.0, this annotation
increment was determined automatically by the program.  Example:  A value of 5
will annotate every 5th trace plotted, a value of 7 will annotate every 7th
trace plotted, etc.  The user may also type AUTO to invoke automatic
determination of the annotation increment.

Application to change Macintosh File-Type:

All files on the Macintosh have associated with them, an attribute called the
"file-type".  These file-types are usually transparent to the user and do not 
necessarily have anything to do with the data contained in the file.  For example,
an application program is USUALLY of file-type "Appl", a document is USUALLY of
file-type "TEXT", etc.  Both TracePlot and TraceCopy require that the SEG-Y
input file have a Macintosh file-type of "TEXT".  This feature has the advantage
making selection of the SEG-Y input file easier, by preventing files which are
not "TEXT" files from being listed in the file selection menu.  Sometimes,
however, a SEG-Y file that is transferred to the Macintosh will not be of
file-type "TEXT" and thus will not appear in the file selection menu.  If you
encounter this problem, use the application "ChangeFileType" which is
included on the Version 2.2 diskette.  Please note that the application only
changes the Macintosh file-type attribute; IT DOES NOT CHANGE THE CONTENTS OF
THE FILE IN ANY WAY.

This application is simple to operate:
It provides a menu which lists files of ALL types;  select the file
whose attribute you wish to change to "TEXT" (double-click the mouse on the
file name, or single click and then click on the OPEN button).  The file's
file-type attribute will immediately be changed to "TEXT".  The last 5 files
selected will be listed below the file selection menu.  Click on "Cancel" to
end the application.  After changing the file-type to "TEXT", that file will
appear in the TracePlot or TraceCopy file selection menu.

Warning!!:  Avoid changing the file-type of other, non-SEG-Y files to "TEXT".
Such a change might cause these files to NOT BE LISTED in the file selection
menu of other applications, if those applications are designed to exclude
"TEXT" file-types from their file selection menu.