segy2grd(1) GMT segy2grd(1)
NAME
segy2grd - Converting SEGY data to a GMT grid
SYNOPSIS
segy2grd segyfile -Ggrdfile
-Iincrement
-Rregion [ -A[n|z] ] [ -D[+xxname][+yyname][+zzname][+sscale][+ooff-
set][+ninvalid][+ttitle][+rremark] ] [ -L[nsamp] ] [ -M[ntraces] ] [
-Nnodata ] [ -Q<mode><value> ] [ -S[header] ] [ -V[level] ] [ -bibi-
nary ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated
arguments.
DESCRIPTION
segy2grd reads an IEEE SEGY file and creates a binary grid file.
Either a simple mapping (equivalent to xyz2grd -Z) or a more compli-
cated averaging where a particular grid cell includes values from more
than one sample in the SEGY file can be done. segy2grd 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.
REQUIRED ARGUMENTS
segyfile is an IEEE floating point SEGY file. Traces are all assumed to
start at 0 time/depth.
-Ggrdfile
grdfile is the name of the binary output grid file.
-I x_inc [and optionally y_inc] is the grid spacing. Append m to
indicate minutes or s to indicate seconds.
-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
[A+-]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 (Carte-
sian) 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.
OPTIONAL ARGUMENTS
-A[n|z]
Add up multiple values that belong to the same node (same as
-Az). Append n to simply count the number of data points that
were assigned to each node. [Default (no -A option) will calcu-
late mean value]. Not used for simple mapping.
-D[+xxname][+yyname][+zzname][+sscale][+ooffset][+ninvalid][+tti-
tle][+rremark]
Give one or more combinations for values xname, yname, zname
(give the names of those variables and in square bracket their
units, e.g., adistance [km]a), scale (to multiply grid values
after read [normally 1]), offset (to add to grid after scaling
[normally 0]), invalid (a value to represent missing data
[NaN]), title (anything you like), and remark (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 (-fg) xname and yname are set automatically.
-L Let nsamp override number of samples in each trace.
-M[ntraces]
Fix number of traces to read in. Default tries to read 10000
traces. -M0 will read number in binary header, -Mntraces will
attempt to read only n traces.
-Nnodata
No data. Set nodes with no input sample to this value [Default
is NaN].
-Q<mode><value>
Can be used to change two different settings depending on mode:
-Qxx-scale applies scalar x-scale to coordinates in trace
header to match the coordinates specified in -R.
-Qys_int specifies sample interval as s_int if incorrect
in the SEGY file.
-S[header]
Set variable spacing; header is c for cdp, o for offset, or
bnumber for 4-byte float starting at byte number. If -S not set,
assumes even spacing of samples at the x_inc, y_inc supplied
with -I.
-V[level] (more a|)
Select verbosity level [c].
-r (more a|)
Set pixel node registration [gridline].
-^ 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 explana-
tion 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.
EXAMPLES
To create a grid file from an even spaced SEGY file test.segy, try
gmt segy2grd test.segy -I0.1/0.1 -Gtest.nc -R198/208/18/25 -V
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
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
gmt segy2grd test.segy -Gtest.nc -R0/100/0/10 -I0.5/0.2 -V -Qx0.1 -Qy0.1
Because the grid interval is larger than the SEGY file sampling, the
individual samples will be averaged in bins
SEE ALSO
gmt(1), grd2xyz(1), grdedit(1), pssegy(1), xyz2grd(1)
COPYRIGHT
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.4.2 Jun 24, 2017 segy2grd(1)
gmt5 5.4.2 - Generated Thu Jun 29 16:18:28 CDT 2017