def load(cls, file: str):
""" Load the Geometry from a SEG-Y file. """
g = cls()
with open(file, 'br') as sgy:
# grab endian, number of traces, sample size, and trace length
endian = gfunc.grab_endiannes(sgy)
nt = gfunc.grab_number_of_traces(sgy)
ss = gfunc.grab_sample_format(sgy)[0]
tl = gfunc.grab_trace_length(sgy)
# skip TFH and BFH
sgy.seek(3600)
# create a matrix to store trace headers' values
data = np.empty(shape=(nt, 90), dtype=np.int32)
for i in range(nt):
# read in, unpack and store the header
raw_header = sgy.read(240)
header = struct.unpack(endian + const.THFS, raw_header[:232])
data[i] = header
# skip to the next header - one trace worth of bytes
sgy.seek(sgy.tell() + ss * tl)
# transform the matrix into a DataFrame
g._df = pd.DataFrame(data, index=range(nt), columns=const.THCOLS)
# apply scalars to elevations and coordinates
g._apply_scalars_after_unpacking()
return g
def test_grab_endiannes(manually_crafted_segy_file,
manually_crafted_little_endian_segy_file):
""" Test the general function for grabbing endiannes. """
# check that the returned value is correct and the the cursor is
# returned to the original position after the grab
with open(manually_crafted_segy_file, 'br') as sgy:
sgy.seek(random.randint(0, 3600))
position = sgy.tell()
assert gfunc.grab_endiannes(sgy) == '>'
assert sgy.tell() == position
with open(manually_crafted_little_endian_segy_file, 'br') as sgy:
sgy.seek(random.randint(0, 3600))
position = sgy.tell()
assert gfunc.grab_endiannes(sgy) == '<'
assert sgy.tell() == position
def load(cls, file: str):
""" Load BFH from a SEG-Y file.
Args:
file (str) : Path to the SEG-Y file to load from.
"""
bfh = cls()
with open(file, 'br') as sgy:
# get the endian
endian = gfunc.grab_endiannes(sgy)
# skip the TFH, read the BFH bytes
sgy.seek(3200)
raw = sgy.read(400)
# unpack and store the values
values = struct.unpack(endian + const.BFHFS, raw)
bfh._dict = dict(zip(const.BFHCOLS, values))
return bfh
def load(cls, file: str):
""" Load the DataMatrix from a SEG-Y file. """
dm = cls()
with open(file, 'br') as sgy:
# grab endian, format letter, trace length, sample size, number of traces, data type, and sample interval
endian = gfunc.grab_endiannes(sgy)
sfc = gfunc.grab_sample_format_code(sgy)
tl = gfunc.grab_trace_length(sgy)
nt = gfunc.grab_number_of_traces(sgy)
si = gfunc.grab_sample_interval(sgy)
ss, fl, _ = const.SFC[sfc]
dtype = const.DTYPEMAP[sfc]
dm._m = np.empty(shape=(nt, tl), dtype=dtype)
sgy.seek(3600)
if sfc == 1: # IBM is a special case
pass
else:
format_string = endian + fl * tl
for i in range(nt):
sgy.seek(sgy.tell() + 240) # skip trace header
raw_trace = sgy.read(ss * tl)
values = struct.unpack(format_string, raw_trace)
dm._m[i] = values
dm.dt = si
dm.t = np.arange(0, si * tl / 1000, si / 1000)
return dm
def load(cls, file: str):
""" Load the SEG-Y file. """
segy = cls()
with open(file, 'br') as sgy:
endian = gfunc.grab_endiannes(sgy)
sfc = gfunc.grab_sample_format_code(sgy)
nt = gfunc.grab_number_of_traces(sgy)
tl = gfunc.grab_trace_length(sgy)
si = gfunc.grab_sample_interval(sgy)
ss, fl, _ = const.SFC[sfc]
dtype = const.DTYPEMAP[sfc]
raw_tfh = sgy.read(3200)
raw_bfh = sgy.read(400)
header_data = np.empty(shape=(nt, 90), dtype=np.int32)
segy.dm._m = np.empty(shape=(nt, tl), dtype=dtype)
if sfc == 1: # IBM is a special case
for i in range(nt):
raw_header = sgy.read(240)
header = struct.unpack(endian + const.THFS,
raw_header[:232])
header_data[i] = header
raw_trace = sgy.read(ss * tl)
trace_values = gfunc.unpack_ibm32_series(raw_trace, endian)
segy.dm._m[i] = trace_values
else:
trace_fs = endian + fl * tl
for i in range(nt):
raw_header = sgy.read(240)
header = struct.unpack(endian + const.THFS,
raw_header[:232])
header_data[i] = header
raw_trace = sgy.read(ss * tl)
trace_values = struct.unpack(trace_fs, raw_trace)
segy.dm._m[i] = trace_values
segy.tfh._contents = raw_tfh.decode('cp500')
bfh_values = struct.unpack(endian + const.BFHFS, raw_bfh)
segy.bfh._dict = dict(zip(const.BFHCOLS, bfh_values))
segy.bfh['no_traces'] = nt
segy.g._df = pd.DataFrame(header_data,
index=range(nt),
columns=const.THCOLS)
segy.g._apply_scalars_after_unpacking()
segy.dm.dt = si
segy.dm.t = np.arange(0, si * tl / 1000, si / 1000)
segy.dm._headers = segy.g
segy.file = file.split('/')[-1]
return segy