NAME
pssegyz - Create imagemasked postscript from SEGY file
SYNOPSIS
pssegyz SEGYfile -Jparameters -Rwest/east/south/north
-F[rgb|gray]|-W [ -I] [ -N ] [ -Bbias ] [ -Cclip ] [ -Z ] [
-Xscale ] [ -Ysample int ] [ -Sheader_x/header_y ] [ -Lnsamp
] [ -Mntrace ] [ -Uredvel ] [ -Eazimuth/elevation ] [ -O ] [
-K ] [ -P ][ -V ]
DESCRIPTION
pssegyz reads a native (IEEE) format SEGY file and produces
a PostScript image of the seismic data. The imagemask opera-
tor is used so that the seismic data are plotted as a 1-bit
deep bitmap in a single (user-specified) color or gray
shade, with a transparent background. The bitmap resolution
is taken from the current GMT defaults. The seismic traces
may be plotted at their true locations using information in
the trace headers (in which case order of the traces in the
file is not significant).
Standard GMT geometry routines are used so that in princi-
ple any map projection may be used, however it is likely
that the geographic projections will lead to unexpected
results. Beware also that some parameters have non-standard
meanings, and a couple of the options for pssegy are not
available in pssegyz.
Note that the order of operations before the seismic data
are plotted is deviation*[clip]([bias]+[normalize](sample
value)). Deviation determines how far in the plot coordi-
nates a [normalized][biased][clipped] sample value of 1
plots from the trace location.
The SEGY file should be a disk image of the tape format (ie
3200 byte text header, which is ignored, 400 byte binary
reel header, and 240 byte header for each trace) with sam-
ples as native real*4 (IEEE real on all the platforms to
which I have access)
SEGYfile
Seismic data set to be imaged
-J Selects the map projection. Scale is inch/degree,
1:xxxxx, or width in inch (upper case modifier).
NON-GEOGRAPHICAL PROJECTIONS:
-Jpscale (Linear projection for polar (theta,r) coordi-
nates)
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and
power scaling)
More details can be found in the psbasemap manpages.
For seismic plots where time or depth increases down-
ward, use a negative y-scale
-R west, east, south, and north specify the Region of
interest. To specify boundaries in degrees and minutes
[and seconds], use the dd:mm[:ss] format. Append r if
lower left and upper right map coordinates are given
instead of wesn.
-F[rgb|gray]
Fill trace (variable area, defaults to filling posi-
tive). rgb or gray gives the color with which the
imagemask is filled.
-W Draw wiggle trace.
Must specify at least one of -W and -F.
OPTIONS
No space between the option flag and the associated argu-
ments.
-I Fill negative rather than positive excursions.
-N Normalize trace by dividing by rms amplitude over full
trace length.
-B Bias to apply to data (added to sample values).
-C Sample value at which to clip data (clipping is applied
to both positive and negative values).
-Z Don't plot traces with zero rms amplitude.
-X Multiply trace locations by scale before plotting.
-Y Override sample interval in reel header.
-S Read trace locations from trace headers: header is
either c for CDP, o for offset, b<num> to read a long
starting at byte <num> in the header (first byte
corresponds to num=0), or a number to fix the location.
First parameter for x, second for y. Default has X and
Y given by trace number.
-L Override number of samples per trace in reel header
(program attempts to determine number of samples from
each trace header if possible to allow for variable
length traces).
-M Override number of traces specified in reel header.
Program detects end of file (relatively) gracefully,
but this parameter limits number of traces that the
program attempts to read.
-U Apply reduction velocity by shifting traces upwards by
redvel/|offset|. Negative velocity removes existing
reduction. Units should be consistent with offset in
trace header and sample interval.
-E Azimuth and elevation for the 3-D projection.
-K More PostScript code will be appended later [Default
terminates the plot system].
-O Selects Overlay plot mode [Default initializes a new
plot system].
-P Selects Portrait plotting mode [GMT Default is
Landscape, see gmtdefaults to change this].
-V Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"].
EXAMPLES
To plot the SEGY file wa1.segy with normalized traces plot-
ted at true offset locations, clipped at +-3 and with wiggle
trace and positive variable area shading in black, try
pssegyz wa1.segy -JX5/-5 -Jz0.05 -E180/5 -R0/100/0/10/0/10
-C3 -N -So -W -F0 > segy.ps
BUGS
Variable area involves filling four-sided figures of dis-
tressing generality. I know that some of the more complex
degenerate cases are not dealt with correctly or at all; the
incidence of such cases increases as viewing angles become
more oblique, and particularly as the viewing elevation
increases. Wiggle-trace plotting is not affected.
SEE ALSO
gmt(l), pssegy(l)