1.. index:: ! segyz
2.. include:: ../module_supplements_purpose.rst_
3
4*******
5segyz
6*******
7
8|segyz_purpose|
9
10Synopsis
11--------
12
13.. include:: ../../common_SYN_OPTs.rst_
14
15**gmt segyz** *SEGYfile* |-J|\ *parameters*
16|-J|\ **z**\|\ **Z**\ *parameters*
17|SYN_OPT-Rz|
18|-D|\ *deviation* |-F|\ [*color*] **-W**
19[ |-C|\ *clip* ]
20[ |-I| ] [ |-L|\ *nsamp* ]
21[ |-M|\ *ntrace* ]
22[ |-N| ]
23[ |-Q|\ *<mode><value>* ]
24[ |-S|\ *header_x*/*header_y* ]
25[ |SYN_OPT-U| ]
26[ |SYN_OPT-V| ]
27[ |SYN_OPT-X| ]
28[ |SYN_OPT-Y| ]
29[ |-Z| ]
30[ |SYN_OPT-p| ]
31[ |SYN_OPT-t| ]
32[ |SYN_OPT--| ]
33
34.. module_common_begins
35
36Description
37-----------
38
39Reads a native (IEEE) format SEGY file and produces a
40plot of the seismic data. The *imagemask* operator is used
41so that the seismic data are plotted as a 1-bit deep bitmap in a single
42(user-specified) color or gray shade, with a transparent background. The
43bitmap resolution is taken from the current GMT defaults. The
44seismic traces may be plotted at their true locations using information
45in the trace headers (in which case order of the traces in the file is
46not significant). Standard GMT geometry routines are used so that in
47principle any map projection may be used, however it is likely that the
48geographic projections will lead to unexpected results. Beware that a
49couple of the options for the 2-D plotter are not available in here.
50
51Note that the order of operations before the seismic data are plotted is
52deviation\*[clip]([bias]+[normalize](sample value)). Deviation
53determines how far *in the plot coordinates* a
54[normalized][biased][clipped] sample value of 1 plots from the trace
55location.
56
57The SEGY file should be a disk image of the tape format (i.e., 3200 byte
58text header, which is ignored, 400 byte binary reel header, and 240 byte
59header for each trace) with samples as native real\*4 (IEEE real on all
60the platforms to which I have access).
61
62Required Arguments
63------------------
64
65*SEGYfile*
66    Seismic SEGY data set to be imaged.
67
68.. |Add_-J| replace:: |Add_-J_links|
69.. include:: /explain_-J.rst_
70    :start-after: **Syntax**
71    :end-before: **Description**
72
73.. _-R:
74
75.. |Add_-Rgeo| unicode:: 0x20 .. just an invisible code
76.. include:: ../../explain_-Rgeo.rst_
77
78.. _-D:
79
80**-D**\ *deviation*
81    gives the deviation in X units of the plot for 1.0 on the scaled
82    trace, This may be a single number (applied equally in X and Y
83    directions) or the pair *devX*\ /*devY*.
84
85.. _-F:
86
87**-F**\ [*color*]
88    Fill trace (variable area, defaults to filling positive). Specify the
89    *color* with which the imagemask is filled.
90
91.. _-W:
92
93**-W**
94    Draw wiggle trace.
95
96You *must* specify at least one of **-W** and **-F**.
97
98Optional Arguments
99------------------
100
101.. _-A:
102
103**-A**
104    Flip the default byte-swap state (default assumes data have a
105    bigendian byte-order).
106
107.. _-C:
108
109**-C**\ *clip*
110    Sample value at which to clip data (clipping is applied to both
111    positive and negative values).
112
113.. _-I:
114
115**-I**
116    Fill negative rather than positive excursions.
117
118.. _-L:
119
120**-L**\ *nsamp*
121    Override number of samples per trace in reel header (program
122    attempts to determine number of samples from each trace header if
123    possible to allow for variable length traces).
124
125.. _-M:
126
127**-M**\ *ntrace*
128    Override number of traces specified in reel header. Program detects
129    end of file (relatively) gracefully, but this parameter limits
130    number of traces that the program attempts to read.
131
132.. _-N:
133
134**-N**
135    Normalize trace by dividing by rms amplitude over full trace length.
136
137.. _-Q:
138
139**-Q**\ *<mode><value>*
140    Can be used to change 5 different settings depending on *mode*:
141       **-Qb**\ *bias* to bias scaled traces (-Qb-0.1 subtracts 0.1 from values).
142
143       **-Qi**\ *dpi* sets the dots-per-inch resolution of the image [300].
144
145       **-Qu**\ *redvel* to apply reduction velocity (negative removes reduction already present).
146
147       **-Qx**\ *mult* to multiply trace locations by *mult*.
148
149       **-Qy**\ *dy* to override sample interval in reel header.
150
151.. _-S:
152
153**-S**\ *header_x*/*header_y*
154    Read trace locations from trace headers: headers is either **c** for CDP,
155    **o** for offset, **b**\ *num* to read a long starting at byte *num* in the
156    header (first byte corresponds to num=0), or a number to fix the
157    location. First parameter for x, second for y. Default has X and Y
158    given by trace number.
159
160.. |Add_-U| replace:: |Add_-U_links|
161.. include:: ../../explain_-U.rst_
162    :start-after: **Syntax**
163    :end-before: **Description**
164
165.. |Add_-V| replace:: |Add_-V_links|
166.. include:: /explain_-V.rst_
167    :start-after: **Syntax**
168    :end-before: **Description**
169
170.. |Add_-XY| replace:: |Add_-XY_links|
171.. include:: ../../explain_-XY.rst_
172    :start-after: **Syntax**
173    :end-before: **Description**
174
175.. _-Z:
176
177**-Z**
178    Do not plot traces with zero rms amplitude.
179
180.. |Add_perspective| unicode:: 0x20 .. just an invisible code
181.. include:: ../../explain_perspective.rst_
182
183.. include:: ../../explain_-t.rst_
184.. include:: ../../explain_help.rst_
185
186.. module_common_ends
187
188Examples
189--------
190
191.. include:: ../../oneliner_info.rst_
192
193To plot the SEGY file wa1.segy with normalized traces plotted at true
194offset locations, clipped at ±3 and with wiggle trace and positive
195variable area shading in black, use
196
197   ::
198
199    gmt segyz wa1.segy -JX5i/-5i -D1 -Jz0.05i -E180/5 -R0/100/0/10/0/10 \
200            -C3 -N -So -W -Fblack -pdf segy
201
202.. module_note_begins
203
204Bugs
205----
206
207Variable area involves filling four-sided figures of distressing
208generality. I *know* that some of the more complex degenerate cases are
209not dealt with correctly or at all; the incidence of such cases
210increases as viewing angles become more oblique, and particularly as the
211viewing elevation increases. Wiggle-trace plotting is not affected.
212
213.. module_note_ends
214
215See Also
216--------
217
218:doc:`gmt </gmt>`,
219:doc:`segy`,
220:doc:`segy2grd`
221