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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
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