segy2grd - Converting SEGY file to grd file format
segy2grd segyfile -Ggrdfile -Ix_inc[/y_inc] -Rwest/east/south/north[r]
[ -A[n|z] ] [ -Dxunit/yunit/zunit/scale/offset/title/remark ] [ -F ] [
-Nnodata ] [ -S[zfile] ] [ -V ] [ -Z[flags] ] [ -: ] [ -bi[s][n] ]
segy2grd reads an IEEE SEGY file and creates a binary grdfile. Either a
simple mapping (equivalent to xyz2grd -Z) or a more complicated averag-
ing 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.
ASCII [or binary] file holding z or (x,y,z) values. xyz triplets
do not have to be sorted (for binary triplets, see -b). 1-column
z tables must be sorted and the -Z must be set).
-G grdfile is the name of the binary output grdfile.
-I x_inc [and optionally y_inc] is the grid spacing. Append m to
indicate minutes or c to indicate seconds.
-R west, east, south, and north specify the Region of interest. To
specify boundaries in degrees and minutes [and seconds], use the
dd:mm[:ss] format. Append r if lower left and upper right map
coordinates are given instead of wesn.
-A 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 Give values for xunit, yunit, zunit, scale, offset, title, and
remark. To leave some of these values untouched, specify = as
-F Force pixel registration [Default is grid registration].
-N No data. Set nodes with no input sample to this value [Default
-S set variable spacing header is c for cdp, o for offset, b<num-
ber> for 4-byte float starting at byte number If -S not set,
assumes even spacing of samples at the dx, dy supplied with -I
-L Override number of samples in each trace
-X applies scalar x-scale to coordinates in trace header to match
the coordinates specified in -R
To create a grdfile from an even spaced SEGY file test.segy, try
segy2grd test.segy -I0.1/0.1 -Gtest.grd -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 grdfile 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
segy2grd test.segy -Gtest.grd -R0/100/0/10 -I0.5/0.2 -V -X0.1
Because the grid interval is larger than the SEGY file sampling,
the individual samples will be averaged in bins
gmt(GMTMANSECTION), grd2xyz(GMTMANSECTION), grdedit(GMTMANSECTION),
GMT4.0 1 Oct 2004 SEGY2GRD(GMTMANSECTION)
Man(1) output converted with