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.TH "SEGY2GRD" "1gmt" "Jan 10, 2019" "5.4.5" "GMT"
.SH NAME
segy2grd \- Converting SEGY data to a GMT grid
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.SH SYNOPSIS
.sp
\fBsegy2grd\fP \fIsegyfile\fP  \fB\-G\fP\fIgrdfile\fP
 \fB\-I\fP\fIincrement\fP
 \fB\-R\fP\fIregion\fP
[  \fB\-A\fP[\fBn\fP|\fBz\fP] ]
[  \fB\-D\fP[\fB+x\fP\fIxname\fP][\fB+y\fP\fIyname\fP][\fB+z\fP\fIzname\fP][\fB+s\fP\fIscale\fP][\fB+o\fP\fIoffset\fP][\fB+n\fP\fIinvalid\fP][\fB+t\fP\fItitle\fP][\fB+r\fP\fIremark\fP] ]
[  \fB\-L\fP[\fInsamp\fP] ]
[  \fB\-M\fP[\fIntraces\fP] ]
[  \fB\-N\fP\fInodata\fP ]
[  \fB\-Q\fP\fI<mode><value>\fP ]
[  \fB\-S\fP[\fIheader\fP] ]
[  \fB\-V\fP[\fIlevel\fP] ]
[ \fB\-bi\fPbinary ]
[ \fB\-:\fP[\fBi\fP|\fBo\fP] ]
.sp
\fBNote:\fP No space is allowed between the option flag and the associated arguments.
.SH DESCRIPTION
.sp
\fBsegy2grd\fP reads an IEEE SEGY file and creates a binary grid file.
Either a simple mapping (equivalent to xyz2grd \-Z) or a more complicated
averaging where a particular grid cell includes values from more than
one sample in the SEGY file can be done. \fBsegy2grd\fP will report if
some of the nodes are not filled in with data. Such unconstrained nodes
are set to a value specified by the user [Default is NaN]. Nodes with
more than one value will be set to the average value.
.SH REQUIRED ARGUMENTS
.sp
\fIsegyfile\fP is an IEEE floating point SEGY file. Traces are all assumed to start at 0 time/depth.
.INDENT 0.0
.TP
\fB\-G\fP\fIgrdfile\fP
\fIgrdfile\fP is the name of the binary output grid file.
.UNINDENT
.INDENT 0.0
.TP
\fB\-I\fP
\fIx_inc\fP [and optionally \fIy_inc\fP] is the grid spacing. Append \fBm\fP
to indicate minutes or \fBs\fP to indicate seconds.
.UNINDENT
.INDENT 0.0
.TP
\fB\-R\fP\fIwest\fP/\fIeast\fP/\fIsouth\fP/\fInorth\fP[/\fIzmin\fP/\fIzmax\fP][\fB+r\fP][\fB+u\fP\fIunit\fP]
\fIwest\fP, \fIeast\fP, \fIsouth\fP, and \fInorth\fP specify the region of interest,
and you may specify them in decimal degrees or in
[±]dd:mm[:ss.xxx][\fBW\fP|\fBE\fP|\fBS\fP|\fBN\fP] format
Append \fB+r\fP if lower left
and upper right map coordinates are given instead of w/e/s/n. The
two shorthands \fB\-Rg\fP and \fB\-Rd\fP stand for global domain (0/360
and \-180/+180 in longitude respectively, with \-90/+90 in latitude).
Alternatively for grid creation, give \fBR\fP\fIcode\fP\fIlon\fP/\fIlat\fP/\fInx\fP/\fIny\fP, where
\fIcode\fP 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 \fIlon\fP/\fIlat\fP coordinate
refers to, and the grid dimensions \fInx\fP and \fIny\fP with grid spacings via
\fB\-I\fP is used to create the corresponding region.
Alternatively, specify the name of an existing grid file and the
\fB\-R\fP settings (and grid spacing, if applicable) are copied from
the grid. Appending \fB+u\fP\fIunit\fP expects projected (Cartesian)
coordinates compatible with chosen \fB\-J\fP and we inversely project
to determine actual rectangular geographic region.
For perspective view (\fB\-p\fP), optionally append /\fIzmin\fP/\fIzmax\fP\&.
In case of perspective view (\fB\-p\fP), a z\-range (\fIzmin\fP, \fIzmax\fP)
can be appended to indicate the third dimension. This needs to be
done only when using the \fB\-Jz\fP option, not when using only the
\fB\-p\fP option. In the latter case a perspective view of the plane is
plotted, with no third dimension.  
.UNINDENT
.SH OPTIONAL ARGUMENTS
.INDENT 0.0
.TP
\fB\-A\fP[\fBn\fP|\fBz\fP]
Add up multiple values that belong to the same node (same as
\fB\-Az\fP). Append \fBn\fP to simply count the number of data points
that were assigned to each node. [Default (no \fB\-A\fP option) will
calculate mean value]. Not used for simple mapping.
.UNINDENT
.INDENT 0.0
.TP
\fB\-D\fP[\fB+x\fP\fIxname\fP][\fB+y\fP\fIyname\fP][\fB+z\fP\fIzname\fP][\fB+s\fP\fIscale\fP][\fB+o\fP\fIoffset\fP][\fB+n\fP\fIinvalid\fP][\fB+t\fP\fItitle\fP][\fB+r\fP\fIremark\fP]
Give one or more combinations for values \fIxname\fP, \fIyname\fP, \fIzname\fP (give the names of those variables
and in square bracket their units, e.g., "distance [km]"), \fIscale\fP (to multiply grid values after
read [normally 1]), \fIoffset\fP (to add to grid after scaling [normally 0]),
\fIinvalid\fP (a value to represent missing data [NaN]), \fItitle\fP (anything you
like), and \fIremark\fP (anything you like). Items not listed will remain untouched.
Give a blank name to completely reset a particular string.
Use quotes to group texts with more than one word.
Note that for geographic grids (\fB\-fg\fP) \fIxname\fP and \fIyname\fP are set automatically.
.UNINDENT
.INDENT 0.0
.TP
\fB\-L\fP
Let \fInsamp\fP override number of samples in each trace.
.UNINDENT
.INDENT 0.0
.TP
\fB\-M\fP[\fIntraces\fP]
Fix number of traces to read in. Default tries to read 10000 traces.
\fB\-M\fP0 will read number in binary header, \fB\-M\fP\fIntraces\fP will
attempt to read only \fIn\fP traces.
.UNINDENT
.INDENT 0.0
.TP
\fB\-N\fP\fInodata\fP
No data. Set nodes with no input sample to this value [Default is
NaN].
.UNINDENT
.INDENT 0.0
.TP
\fB\-Q\fP\fI<mode><value>\fP
.INDENT 7.0
.TP
.B Can be used to change two different settings depending on \fImode\fP:
\fB\-Qx\fP\fIx\-scale\fP applies scalar \fIx\-scale\fP to coordinates in trace
header to match the coordinates specified in \-R.
.sp
\fB\-Qy\fP\fIs_int\fP specifies sample interval as \fIs_int\fP if incorrect in the SEGY file.
.UNINDENT
.UNINDENT
.INDENT 0.0
.TP
\fB\-S\fP[\fIheader\fP]
Set variable spacing; \fIheader\fP is \fBc\fP for cdp, \fBo\fP for offset, or \fBb\fP\fInumber\fP
for 4\-byte float starting at byte \fInumber\fP\&. If \fB\-S\fP not set, assumes even
spacing of samples at the \fIx_inc, y_inc\fP supplied with \fB\-I\fP\&.
.UNINDENT
.INDENT 0.0
.TP
\fB\-V\fP[\fIlevel\fP] (more ...)
Select verbosity level [c].  
.UNINDENT
.INDENT 0.0
.TP
\fB\-r\fP (more ...)
Set pixel node registration [gridline].  
.UNINDENT
.INDENT 0.0
.TP
\fB\-^\fP or just \fB\-\fP
Print a short message about the syntax of the command, then exits (NOTE: on Windows just use \fB\-\fP).
.TP
\fB\-+\fP or just \fB+\fP
Print an extensive usage (help) message, including the explanation of
any module\-specific option (but not the GMT common options), then exits.
.TP
\fB\-?\fP or no arguments
Print a complete usage (help) message, including the explanation of all options, then exits.
.UNINDENT
.SH EXAMPLES
.sp
To create a grid file from an even spaced SEGY file test.segy, try
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.sp
.nf
.ft C
gmt segy2grd test.segy \-I0.1/0.1 \-Gtest.nc \-R198/208/18/25 \-V
.ft P
.fi
.UNINDENT
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.UNINDENT
.UNINDENT
.sp
Note that this will read in 18\-25s (or km) on each trace, but the
first trace will be assumed to be at X=198
.sp
To create a grid file from the SEGY file test.segy, locating traces
according to the CDP number, where there are 10 CDPs per km and the
sample interval is 0.1, try
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.sp
.nf
.ft C
gmt segy2grd test.segy \-Gtest.nc \-R0/100/0/10 \-I0.5/0.2 \-V \-Qx0.1 \-Qy0.1
.ft P
.fi
.UNINDENT
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.UNINDENT
.UNINDENT
.sp
Because the grid interval is larger than the SEGY file sampling, the
individual samples will be averaged in bins
.SH SEE ALSO
.sp
gmt, grd2xyz,
grdedit, pssegy,
xyz2grd
.SH COPYRIGHT
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
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