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import sys
import numpy as np
import segyio
def main():
if len(sys.argv) < 7:
sys.exit("Usage: {} [file] [samples] [first iline] [last iline] [first xline] [last xline]".format(sys.argv[0]))
spec = segyio.spec()
filename = sys.argv[1]
# to create a file from nothing, we need to tell segyio about the structure of
# the file, i.e. its inline numbers, crossline numbers, etc. You can also add
# more structural information, but offsets etc. have sensible defautls. This is
# the absolute minimal specification for a N-by-M volume
spec.sorting = 2
spec.format = 1
spec.samples = range(int(sys.argv[2]))
spec.ilines = range(*map(int, sys.argv[3:5]))
spec.xlines = range(*map(int, sys.argv[5:7]))
with segyio.create(filename, spec) as f:
# one inline consists of 50 traces
# which in turn consists of 2000 samples
start = 0.0
step = 0.00001
# fill a trace with predictable values: left-of-comma is the inline
# number. Immediately right of comma is the crossline number
# the rightmost digits is the index of the sample in that trace meaning
# looking up an inline's i's jth crosslines' k should be roughly equal
# to i.j0k
trace = np.arange(start = start,
stop = start + step * len(spec.samples),
step = step,
dtype = np.single)
# one inline is N traces concatenated. We fill in the xline number
line = np.concatenate([trace + (xl / 100.0) for xl in spec.xlines])
line = line.reshape( (len(spec.xlines), len(spec.samples)) )
# write the line itself to the file
# write the inline number in all this line's headers
for ilno in spec.ilines:
f.iline[ilno] = (line + ilno)
f.header.iline[ilno] = { segyio.TraceField.INLINE_3D: ilno,
segyio.TraceField.offset: 1
}
# then do the same for xlines
for xlno in spec.xlines:
f.header.xline[xlno] = { segyio.TraceField.CROSSLINE_3D: xlno }
if __name__ == '__main__':
main()
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