pssegyz - Create imagemasked postscript from SEGY file
pssegyz SEGYfile -Jparameters
-Jz|Zparameters
-Rwest/east/south/north[/zmin/zmax][+r]
-Ddeviation -F[color] -W [
-Cclip ] [ -I ] [ -K ] [ -Lnsamp ]
[ -Mntrace ] [ -N ] [ -O ] [ -P ] [
-Q<mode><value> ] [
-Sheader_x/header_y ] [ -U[stamp] ] [
-V[level] ] [ -Xx_offset ] [
-Yy_offset ] [ -Z ] [ -pflags ] [
-ttransp ]
Note: No space is allowed between the option flag and the
associated arguments.
pssegyz reads a native (IEEE) format SEGY file and produces
a PostScript image of the seismic data. The imagemask operator 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 principle any map
projection may be used, however it is likely that the geographic projections
will lead to unexpected results. Beware that 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 coordinates 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 (i.e.,
3200 byte text header, which is ignored, 400 byte binary reel header, and
240 byte header for each trace) with samples as native real*4 (IEEE real on
all the platforms to which I have access).
- SEGYfile
- Seismic SEGY data set to be imaged.
- -Rwest/east/south/north[/zmin/zmax][+r][+uunit]
- west, east, south, and north specify the
region of interest, and you may specify them in decimal degrees or in
[±]dd:mm[:ss.xxx][W|E|S|N] format
Append +r if lower left and upper right map coordinates are given
instead of w/e/s/n. The two shorthands -Rg and -Rd stand for
global domain (0/360 and -180/+180 in longitude respectively, with -90/+90
in latitude). Alternatively for grid creation, give
Rcodelon/lat/nx/ny, where
code is a 2-character combination of L, C, R (for left, center, or
right) and T, M, B for top, middle, or bottom. e.g., BL for lower left.
This indicates which point on a rectangular region the
lon/lat coordinate refers to, and the grid dimensions
nx and ny with grid spacings via -I is used to create
the corresponding region. Alternatively, specify the name of an existing
grid file and the -R settings (and grid spacing, if applicable) are
copied from the grid. Appending +uunit expects projected
(Cartesian) coordinates compatible with chosen -J and we inversely
project to determine actual rectangular geographic region. For perspective
view (-p), optionally append /zmin/zmax. In case of
perspective view (-p), a z-range (zmin, zmax) can be
appended to indicate the third dimension. This needs to be done only when
using the -Jz option, not when using only the -p option. In
the latter case a perspective view of the plane is plotted, with no third
dimension.
- -Ddeviation
- gives the deviation in X units of the plot for 1.0 on the scaled trace,
This may be a single number (applied equally in X and Y directions) or the
pair devX/devY.
- -F[color]
- Fill trace (variable area, defaults to filling positive). Specify the
color with which the imagemask is filled.
You must specify at least one of -W and
-F.
- -A
- Flip the default byte-swap state (default assumes data have a bigendian
byte-order).
- -Cclip
- Sample value at which to clip data (clipping is applied to both positive
and negative values).
- -I
- Fill negative rather than positive excursions.
- -Lnsamp
- 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).
- -Mntrace
- 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.
- -N
- Normalize trace by dividing by rms amplitude over full trace length.
- -Sheader_x/header_y
- Read trace locations from trace headers: headers 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.
-X[a|c|f|r][x-shift[u]]
- -Z
- Do not plot traces with zero rms amplitude.
- -^ or just -
- Print a short message about the syntax of the command, then exits (NOTE:
on Windows just use -).
- -+ or just +
- Print an extensive usage (help) message, including the explanation of any
module-specific option (but not the GMT common options), then exits.
- -? or no arguments
- Print a complete usage (help) message, including the explanation of all
options, then exits.
To plot the SEGY file wa1.segy with normalized traces plotted at
true offset locations, clipped at +/-3 and with wiggle trace and positive
variable area shading in black, use
gmt pssegyz wa1.segy -JX5i/-5i -D1 -Jz0.05i -E180/5 -R0/100/0/10/0/10 \
-C3 -N -So -W -Fblack > segy.ps
Variable area involves filling four-sided figures of distressing
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.
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F.
Wobbe