1SEGY2GRD(1) Generic Mapping Tools SEGY2GRD(1)
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6 segy2grd - Converting SEGY file to grid file format
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9 segy2grd segyfile -Ggrdfile -Ixinc[unit][=|+][/yinc[unit][=|+]]
10 -Rwest/east/south/north[r] [ -A[n|z] ] [ -Dxname/yname/zname/scale/off‐
11 set/title/remark ] [ -F ] [ -Nnodata ] [ -S[zfile] ] [ -V ] [
12 -Z[flags] ] [ -:[i|o] ] [ -bi[s|S|d|D[ncol]|c[var1/...]] ]
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15 segy2grd reads an IEEE SEGY file and creates a binary grid file. Either
16 a simple mapping (equivalent to xyz2grd -Z) or a more complicated aver‐
17 aging where a particular grid cell includes values from more than one
18 sample in the SEGY file can be done. segy2grd will report if some of
19 the nodes are not filled in with data. Such unconstrained nodes are set
20 to a value specified by the user [Default is NaN]. Nodes with more
21 than one value will be set to the average value.
22 segyfile
24 ASCII [or binary] file holding z or (x,y,z) values. xyz triplets
25 do not have to be sorted (for binary triplets, see -b). 1-column
26 z tables must be sorted and the -Z must be set).
27 -G grdfile is the name of the binary output grid file.
29 -I x_inc [and optionally y_inc] is the grid spacing. Append m to
31 indicate minutes or c to indicate seconds.
32 -R west, east, south, and north specify the Region of interest, and
34 you may specify them in decimal degrees or in
35 [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower left and
36 upper right map coordinates are given instead of w/e/s/n. The
37 two shorthands -Rg and -Rd stand for global domain (0/360 and
38 -180/+180 in longitude respectively, with -90/+90 in latitude).
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41 -A Add up multiple values that belong to the same node (same as
42 -Az). Append n to simply count the number of data points that
43 were assigned to each node. [Default (no -A option) will calcu‐
44 late mean value]. Not used for simple mapping.
45 -D Give values for xname, yname, zname, scale, offset, title, and
47 remark. To leave some of these values untouched, specify = as
48 the value.
49 -F Force pixel registration [Default is grid registration].
51 -N No data. Set nodes with no input sample to this value [Default
53 is NaN].
54 -S set variable spacing header is c for cdp, o for offset, b<num‐
56 ber> for 4-byte float starting at byte number If -S not set,
57 assumes even spacing of samples at the dx, dy supplied with -I
58 -L Override number of samples in each trace
60 -X applies scalar x-scale to coordinates in trace header to match
62 the coordinates specified in -R
63 -Y Specifies sample interval as s_int if incorrect in the SEGY file
65 -M Fix number of traces to read in. Default tries to read 10000
67 traces. -M0 will read number in binary header, -Mn will attempt
68 to read only n traces.
69 -V Selects verbose mode, which will send progress reports to stderr
71 [Default runs "silently"].
72 EXAMPLES
75 To create a grid file from an even spaced SEGY file test.segy,
76 try
77 segy2grd test.segy -I0.1/0.1 -Gtest.grd -R198/208/18/25 -V
79 Note that this will read in 18-25s (or km) on each trace, but
81 the first trace will be assumed to be at X=198
82 To create a grid file from the SEGY file test.segy, locating
84 traces according to the CDP number, where there are 10 CDPs per
85 km and the sample interval is 0.1, try
86 segy2grd test.segy -Gtest.grd -R0/100/0/10 -I0.5/0.2 -V -X0.1
88 -Y0.1
89 Because the grid interval is larger than the SEGY file sampling,
91 the individual samples will be averaged in bins
92
94 GMT(1), grd2xyz(1), grdedit(1), pssegy(1)
95GMT 4.3.1 15 May 2008 SEGY2GRD(1)