class CustomTraceHeader(TraceHeaderRev1):
unassigned_1 = field(
Int16, offset=233, default=0, documentation="Unassigned 1")
unassigned_2 = field(
Int16, offset=235, default=0, documentation="Unassigned 2")
unassigned_3 = field(
Int16, offset=237, default=0, documentation="Unassigned 3")
unassigned_4 = field(
Int16, offset=239, default=0, documentation="Unassigned 4")
class ExampleHeader(Header):
field_a = field(Int32,
offset=1,
default=0,
documentation="""Field A. This is field A.""")
field_b = field(NNInt32,
offset=5,
default=42,
documentation="Field B. This is field B.")
field_c = field(Int32,
offset=9,
default=-1,
documentation="Field C. This is field C.")
class SegyTraceHeaderFormat(TraceHeaderRev1):
field_record_num = field(
Int32,
offset=record_byte,
default=0,
documentation=
"Original field record number. Highly recommended for all types of data."
)
trace_num = field(
Int32,
offset=trace_byte,
default=0,
documentation=
"Trace number within the original field record. Highly recommended for all types of data."
)
class CustomBinaryReelHeader(BinaryReelHeader):
num_samples = field(
UInt16,
offset=3221,
default=0,
documentation=
"""Number of samples per data trace. Mandatory for all types of data.
Note: The sample interval and number of samples in the Binary File Header should be for the primary set of
seismic data traces in the file.""")
class BinaryReelHeader(Header):
START_OFFSET_IN_BYTES = 3201
LENGTH_IN_BYTES = 400
job_id_num = field(Int32,
offset=3201,
default=0,
documentation="Job identification number")
line_num = field(
NNInt32,
offset=3205,
default=0,
documentation=
"Line number. For 3-D poststack data, this will typically contain the in-line number."
)
reel_num = field(Int32,
offset=3209,
default=0,
documentation="Reel number.")
data_traces_per_ensemble = field(
NNInt16,
offset=3213,
default=0,
documentation=
"Number of data traces per ensemble. Mandatory for prestack data.")
auxiliary_traces_per_ensemble = field(
NNInt16,
offset=3215,
default=0,
documentation=
"Number of auxiliary traces per ensemble. Mandatory for prestack data."
)
sample_interval = field(
NNInt16,
offset=3217,
default=0,
documentation=
"Sample interval in microseconds (μs). Mandatory for all data types.")
original_field_sample_interval = field(
NNInt16,
offset=3219,
default=0,
documentation=
"Sample interval in microseconds (μs) of original field recording.")
num_samples = field(
NNInt16,
offset=3221,
default=0,
documentation=
"""Number of samples per data trace. Mandatory for all types of data.
Note: The sample interval and number of samples in the Binary File Header should be for the primary set of
seismic data traces in the file.""")
original_field_num_samples = field(
NNInt16,
offset=3223,
default=0,
documentation=
"Number of samples per data trace for original field recording.")
data_sample_format = field(DataSampleFormatField,
offset=3225,
default=5,
documentation=DataSampleFormat.__doc__)
ensemble_fold = field(
NNInt16,
offset=3227,
default=0,
documentation=
"""Ensemble fold. The expected number of data traces per trace ensemble (e.g. the CMP fold).
Highly recommended for all types of data.""")
trace_sorting = field(TraceSortingField,
offset=3229,
default=0,
documentation=TraceSorting.__doc__)
vertical_sum_code = field(NNInt16,
offset=3231,
default=0,
documentation="""Vertical sum code:
1 = no sum,
2 = two sum,
...,
N=M-1 sum (M=2to32,767).""")
sweep_frequency_at_start = field(
NNInt16,
offset=3233,
default=0,
documentation="Sweep frequency at start (Hz).")
sweep_frequency_at_end = field(
NNInt16,
offset=3235,
default=0,
documentation="Sweep frequency at end (Hz).")
sweep_length = field(NNInt16,
offset=3237,
default=0,
documentation="Sweep length in milliseconds.")
sweep_type = field(segpy.trace_header.SweepTypeField,
offset=3239,
default=0,
documentation=segpy.trace_header.SweepType.__doc__)
sweep_trace_number = field(Int16,
offset=3241,
default=0,
documentation="Trace number of sweep channel.")
sweep_trace_taper_length_at_start = field(
NNInt16,
offset=3243,
default=0,
documentation="Sweep trace taper length at start in milliseconds.")
sweep_trace_taper_length_at_end = field(
NNInt16,
offset=3245,
default=0,
documentation="Sweep trace taper length at end in milliseconds.")
taper_type = field(segpy.trace_header.TaperTypeField,
offset=3247,
default=0,
documentation=segpy.trace_header.TaperType.__doc__)
correlated_data_traces = field(CorrelatedDataTracesField,
offset=3249,
default=0,
documentation=CorrelatedDataTraces.__doc__)
binary_gain_recovered = field(BinaryGainRecoveredField,
offset=3251,
default=0,
documentation=BinaryGainRecovered.__doc__)
amplitude_recovery_method = field(
AmplitudeRecoveryMethodField,
offset=3253,
default=0,
documentation=AmplitudeRecoveryMethod.__doc__)
measurement_system = field(MeasurementSystemField,
offset=3255,
default=0,
documentation=MeasurementSystem.__doc__)
impulse_signal_polarity = field(
ImpulseSignalPolarityField,
offset=3257,
default=0,
documentation=ImpulseSignalPolarity.__doc__)
vibratory_polarity_code = field(
VibratoryPolarityCodeField,
offset=3259,
default=0,
documentation=VibratoryPolarityCode.__doc__)
format_revision_num = field(
FormatRevisionNumField,
offset=3501,
default=0x100,
documentation=
"""SEG Y Format Revision Number. This is a 16-bit unsigned value with a Q-
point between the first and second bytes. Thus for SEG Y Revision 1.0,
as defined in this document, this will be recorded as 010016. This
field is mandatory for all versions of SEG Y, although a value of zero
indicates “traditional” SEG Y conforming to the 1975 standard.""")
fixed_length_trace_flag = field(FixedLengthTraceFlagField,
offset=3503,
default=0,
documentation=FixedLengthTraceFlag.__doc__)
num_extended_textual_headers = field(
NumExtendedTextualHeadersField,
offset=3505,
default=0,
documentation=
"""Number of 3200-byte, Extended Textual File Header records following the
Binary Header. A value of zero indicates there are no Extended Textual
File Header records (i.e. this file has no Extended Textual File
Header(s)). A value of -1 indicates that there are a variable number of
Extended Textual File Header records and the end of the Extended
Textual File Header is denoted by an ((SEG: EndText)) stanza in the
final record. A positive value indicates that there are exactly that
many Extended Textual File Header records. Note that, although the
exact number of Extended Textual File Header records may be a useful
piece of information, it will not always be known at the time the
Binary Header is written and it is not mandatory that a positive value
be recorded here. This field is mandatory for all versions of SEG Y,
although a value of zero indicates “traditional” SEG Y conforming to
the 1975 standard.""")
class TraceHeaderRev1(TraceHeaderRev0):
cdp_x = field(
Int32, offset=181, default=0, documentation=
"""X coordinate of ensemble (CDP) position of this trace. The coordinate
reference system should be identified through an extended header
Location Data stanza. The xy_scalar field applies to this value."""
)
cdp_y = field(
Int32, offset=185, default=0, documentation=
"""Y coordinate of ensemble (CDP) position of this trace. The coordinate
reference system should be identified through an extended header
Location Data stanza. The xy_scalar field applies to this value."""
)
inline_number = field(
Int32, offset=189, default=0, documentation=
"""In-line number for 3-D poststack data. If one in-line per SEG Y file is
being recorded, this value should be the same for all traces in the
file and the same value will be recorded in bytes 3205-3208 of the
Binary File Header.""" # TODO: replace bytes with field name
)
crossline_number = field(
Int32, offset=193, default=0, documentation=
"""Cross-line number for 3-D poststack data. This will typically be the same
value as the ensemble (CDP) number in Trace Header ensemble_num field,
but this does not have to be the case."""
)
shotpoint_number = field(
Int32, offset=197, default=0, documentation=
"""Shotpoint number. This is probably only applicable to 2-D poststack data.
Note that it is assumed that the shotpoint number refers to the source
location nearest to the ensemble (CDP) location for a particular trace.
If this is not the case, there should be a comment in the Textual File
Header explaining what the shotpoint number actually refers to."""
)
shotpoint_scalar = field(
Int16, offset=201, default=0, documentation=
"""Scalar to be applied to the shotpoint number in trace header field
shotpoint_number to give the real value. If positive, scalar is used as
a multiplier; if negative as a divisor; if zero the shotpoint number is
not scaled (i.e. it is an integer. A typical value will be -10,
allowing shotpoint numbers with one decimal digit to the right of the
decimal point)."""
)
trace_unit = field(
SampleUnitField, offset=203, default=0,
documentation="Trace value measurement unit:\n{}".format(SampleUnit.__doc__)
)
transduction_constant_mantissa = field(
Int32, offset=205, default=0, documentation=
"""Transduction Constant mantissa. The mantissa of the multiplicative constant
used to convert the Data Trace samples to the Transduction Units
(specified in Trace Header transduction_units field). The mantissa of
the constant is encoded as a four-byte, two's complement integer. The
constant value is given by transduction_constant_mantissa *
10**transduction_constant_exponent."""
)
transduction_constant_exponent = field(
Int16, offset=209, default=0, documentation=
"""Transduction Constant exponent. The base 10 exponent of the multiplicative
constant used to convert the Data Trace samples to the Transduction
Units (specified in Trace Header transduction_units field). The
constant value is given by transduction_constant_mantissa *
10**transduction_constant_exponent."""
)
transduction_units = field(
SampleUnitField, offset=211, default=0, documentation=
"""Transduction Units. The unit of measurement of the Data Trace samples after
they have been multiplied by the Transduction Constant specified in
Trace Header fields transduction_constant_mantissa and
transduction_constant_exponent.\n{}""".format(SampleUnit.__doc__)
)
device_trace_identifier = field(
Int16, offset=213, default=0, documentation=
"""Device/Trace Identifier — The unit number or id number of the device
associated with the Data Trace (i.e. 4368 for vibrator serial number
4368 or 20316 for gun 16 on string 3 on vessel 2). This field allows
traces to be associated across trace ensembles independently of the
trace number (ensemble_trace_num field)."""
)
time_scalar = field(
ScalarFactorField, offset=215, default=0, documentation=
"""Scalar to be applied to times specified in Trace Header fields
uphole_time_at_source, uphole_time_at_group, source_static_correction,
group_static_correction, total_static, lag_time_a, lag_time_b,
delay_recording_time, mute_start_time, mute_end_time to give the true
time value in milliseconds. Scalar = 1, +10, +100, +1000, or +10,000.
If positive, scalar is used as a multiplier; if negative, scalar is
used as divisor. A value of zero is assumed to be a scalar value of
1."""
)
source_type = field(
SourceTypeField, offset=217, default=0,
documentation=SourceTypeField.__doc__
)
source_energy_direction = field(
Int32, offset=219, default=0, documentation= # TODO: This is six bytes. What is the format?
"""Source Energy Direction with respect to the source orientation. The positive
orientation direction is defined in Bytes 217-218 of the Trace Header.
The energy direction is encoded in tenths of degrees (i.e. 347.8° is
encoded as 3478)."""
)
source_measurement_mantissa = field(
Int32, offset=225, default=0, documentation=
"""Source Measurement mantissa. Describes the source effort used to generate
the trace. The measurement can be simple, qualitative measurements such
as the total weight of explosive used or the peak air gun pressure or
the number of vibrators times the sweep duration. Although these simple
measurements are acceptable, it is preferable to use true measurement
units of energy or work. The constant is encoded as a four-byte, two's
complement integer (source_measurement_mantissa) and a two-byte, two's
complement integer source_measurement_exponent) which is the power of
ten exponent (i.e. source_measurement_mantissa *
10**source_measurement_exponent)."""
)
source_measurement_exponent = field(
Int16, offset=229, default=0, documentation=
"""Source Measurement exponent. Describes the source effort used to generate
the trace. The measurement can be simple, qualitative measurements such
as the total weight of explosive used or the peak air gun pressure or
the number of vibrators times the sweep duration. Although these simple
measurements are acceptable, it is preferable to use true measurement
units of energy or work. The constant is encoded as a four-byte, two's
complement integer (source_measurement_mantissa) and a two-byte, two's
complement integer source_measurement_exponent) which is the power of
ten exponent (i.e. source_measurement_mantissa *
10**source_measurement_exponent)."""
)
source_measurement_unit = field(
SourceMeasurementUnitField, offset=231, default=0,
documentation=SourceMeasurementUnit.__doc__
)
class TraceHeaderRev0(Header):
START_OFFSET_IN_BYTES = 1
LENGTH_IN_BYTES = 240
line_sequence_num = field(
Int32, offset=1, default=0, documentation=
"""Trace sequence number within line — Numbers continue to increase if the same
line continues across multiple SEG Y files. Highly recommended for all
types of data. [Usually starts at one for each reel.]""")
file_sequence_num = field(
Int32, offset=5, default=0, documentation=
"Trace sequence number within SEG Y file — Each file starts with trace sequence one.")
field_record_num = field(
Int32, offset=9, default=0, documentation=
"Original field record number. Highly recommended for all types of data.")
trace_num = field(
Int32, offset=13, default=0, documentation=
"Trace number within the original field record. Highly recommended for all types of data.")
energy_source_point_num = field(
Int32, offset=17, default=0, documentation=
"""Energy source point number — Used when more than one record occurs at the
same effective surface location. It is recommended that the new entry
defined in Trace Header bytes 197-202 be used for shotpoint number.""")
ensemble_num = field(
Int32, offset=21, default=0, documentation=
"Ensemble number (i.e. CDP , CMP , CRP , etc)")
ensemble_trace_num = field(
NNInt32, offset=25, default=0, documentation=
"Trace number within the ensemble — Each ensemble starts with trace number one.")
trace_identification_code = field(
Int16, offset=29, default=0, documentation=
"Trace identification code")
num_vertically_summed_traces = field(
NNInt16, offset=31, default=1, documentation=
"Number of vertically summed traces yielding this trace. (1 is one trace, 2 is two summed traces, etc.)")
num_horizontally_stacked_traces = field(
NNInt16, offset=33, default=1, documentation=
"Number of horizontally stacked traces yielding this trace. (1 is one trace, 2 is two stacked traces, etc.)")
data_use = field(
DataUseField, offset=35, default=1,
documentation=DataUse.__doc__)
doc_nreceiver_offset = field(
Int32, offset=37, default=0, documentation=
"""Distance from center of the source point to the center of the receiver group
(negative if opposite to direction in which line is shot).""")
receiver_group_elevation = field(
Int32, offset=41, default=0, documentation=
"""Receiver group elevation (all elevations above the Vertical datum are
positive and below are negative). The elevation_scalar applies to this
value.""")
surface_elevation_at_source = field(
Int32, offset=45, default=0, documentation=
"Surface elevation at source. The elevation_scalar applies to this value.")
source_depth_below_surface = field(
NNInt32, offset=49, default=0, documentation=
"Source depth below surface (a positive number). The elevation_scalar applies to this value.")
datum_elevation_at_receiver_group = field(
NNInt32, offset=53, default=0, documentation=
"Source depth below surface (a positive number). The elevation_scalar applies to this value.")
datum_elevation_at_source = field(
Int32, offset=57, default=0, documentation=
"Datum elevation at source. The elevation_scalar applies to this value.")
water_depth_at_source = field(
Int32, offset=61, default=0, documentation=
"Water depth at source. The elevation_scalar applies to this value.")
water_depth_at_group = field(
Int32, offset=65, default=0, documentation=
"Water depth at group. The elevation_scalar applies to this value."
)
elevation_scalar = field(
ScalarFactorField, offset=69, default=ScalarFactor.POS_1,
documentation=
"""Scalar to be applied to the elevations and depths specified in:
receiver_group_elevation, surface_elevation_at_source,
source_depth_below_surface, datum_elevation_at_receiver_group,
datum_elevation_at_source, water_depth_at_source and
water_depth_at_group, to give the real value. Scalar = 1, +10, +100,
+1000, or +10,000. If positive, scalar is used as a multiplier; if
negative, scalar is used as a divisor."""
)
xy_scalar = field(
ScalarFactorField, offset=71, default=ScalarFactor.POS_1, documentation=
"""Scalar to be applied to all coordinates specified in source_x, source_y,
group_x, group_y, cdp_x and cdp_y to give the real value. Scalar = 1,
+10, +100, +1000, or +10,000. If positive, scalar is used as a
multiplier; if negative, scalar is used as divisor."""
)
source_x = field(
Int32, offset=73, default=0, documentation=
"""Source coordinate - X. The xy_scalar applies to this value. The coordinate
reference system should be identified through an extended header
Location Data stanza. If the coordinate units are in seconds of arc,
decimal degrees or DMS, the X values represent longitude. A positive
value designates east of Greenwich Meridian and a negative value
designates west."""
)
source_y = field(
Int32, offset=77, default=0, documentation=
"""Source coordinate - Y. The xy_scalar applies to this value. The coordinate
reference system should be identified through an extended header
Location Data stanza. If the coordinate units are in seconds of arc,
decimal degrees or DMS, the Y values represent latitude. A positive
value designates north of the equator and a negative value designates
south."""
)
group_x = field(
Int32, offset=81, default=0, documentation=
"""Group coordinate - X. The xy_scalar applies to this value. The coordinate
reference system should be identified through an extended header
Location Data stanza. If the coordinate units are in seconds of arc,
decimal degrees or DMS, the X values represent longitude. A positive
value designates east of Greenwich Meridian and a negative value
designates west."""
)
group_y = field(
Int32, offset=85, default=0, documentation=
"""Source coordinate - Y. The xy_scalar applies to this value. The coordinate
reference system should be identified through an extended header
Location Data stanza. If the coordinate units are in seconds of arc,
decimal degrees or DMS, the Y values represent latitude. A positive
value designates north of the equator and a negative value designates
south."""
)
coordinate_units = field(
CoordinateUnitsField, offset=89, default=0,
documentation=CoordinateUnits.__doc__
)
weathering_velocity = field(
NNInt16, offset=91, default=0, documentation=
"Weathering velocity. (ft/s or m/s as specified in Binary File Header bytes 3255- 3256)" # TODO
)
subweathering_velocity = field(
NNInt16, offset=93, default=0, documentation=
"Subweathering velocity. (ft/s or m/s as specified in Binary File Header bytes 3255-3256)" # TODO
)
uphole_time_at_source = field(
NNInt16, offset=95, default=0, documentation=
"Uphole time at source in milliseconds. The time_scalar applies to this value."
)
uphole_time_at_group = field(
NNInt16, offset=97, default=0, documentation=
"Uphole time at group in milliseconds. The time_scalar applies to this value."
)
source_static_correction = field(
Int16, offset=99, default=0, documentation=
"Source static correction in milliseconds. The time_scalar applies to this value."
)
group_static_correction = field(
Int16, offset=101, default=0, documentation=
"Group static correction in milliseconds. The time_scalar applies to this value."
)
total_static = field(
Int16, offset=103, default=0, documentation=
"""Total static applied in milliseconds. (Zero if no static has been applied).
The time_scalar applies to this value."""
)
lag_time_a = field(
Int16, offset=105, default=0, documentation=
"""Lag time A. Time in milliseconds between end of 240-byte trace
identification header and time break. The value is positive if time
break occurs after the end of header; negative if time break occurs
before the end of header. Time break is defined as the initiation pulse
that may be recorded on an auxiliary trace or as otherwise specified by
the recording system. The time_scalar applies to this value."""
)
lag_time_b = field(
Int16, offset=107, default=0, documentation=
"""Lag Time B. Time in milliseconds between time break and the initiation time
of the energy source. May be positive or negative. The time_scalar
applies to this value."""
)
delay_recording_time = field(
Int16, offset=109, default=0, documentation=
"""Delay recording time — Time in milliseconds between initiation time of
energy source and the time when recording of data samples begins. In
SEG Y rev 0 this entry was intended for deep-water work if data
recording does not start at zero time. The entry can be negative to
accommodate negative start times (i.e. data recorded before time zero,
presumably as a result of static application to the data trace). If a
non-zero value (negative or positive) is recorded in this entry, a
comment to that effect should appear in the Textual File Header. The
time_scalar applies to this value."""
)
mute_start_time = field(
NNInt16, offset=111, default=0, documentation=
"Mute time — Start time in milliseconds. The time_scalar applies to this value."
)
mute_end_time = field(
NNInt16, offset=113, default=0, documentation=
"Mute time — End time in milliseconds. The time_scalar applies to this value."
)
num_samples = field(
NNInt16, offset=115, default=0, documentation=
"Number of samples in this trace. Highly recommended for all types of data."
)
sample_interval = field(
Int16, offset=117, default=0, documentation=
"""Sample interval in microseconds (μs) for this trace. The number of bytes in
a trace record must be consistent with the number of samples written in
the trace header. This is important for all recording media; but it is
particularly crucial for the correct processing of SEG Y data in disk
files (see Appendix C). If the fixed length trace flag in bytes
3503-3504 of the Binary File Header is set, the sample interval and
#TODO: field names instead of byte offsets number of samples in every
trace in the SEG Y file must be the same as the values recorded in the
Binary File Header. If the fixed length trace flag is not set, the
sample interval and number of samples may vary from trace to trace.
Highly recommended for all types of data."""
)
gain_type_of_field_instruments = field(
NNInt16, offset=119, default=0, documentation=
"Gain type of field instruments. 1 = fixed, 2 = binary, 3 = floating point, 4 ... N = optional use."
)
instrument_gain_constant = field(
Int16, offset=121, default=0, documentation=
"Instrument gain constant (dB)."
)
instrument_initial_gain = field(
Int16, offset=123, default=0, documentation=
"Instrument early or initial gain (dB)."
)
correlated = field(
CorrelatedField, offset=125, default=1,
documentation=Correlated.__doc__
)
sweep_frequency_at_start = field(
NNInt16, offset=127, default=0, documentation=
"Sweep frequency at start (Hz)."
)
sweep_frequency_at_end = field(
NNInt16, offset=129, default=0, documentation=
"Sweep frequency at end (Hz)."
)
sweep_length = field(
NNInt16, offset=131, default=0, documentation=
"Sweep length in milliseconds."
)
sweep_type = field(
SweepTypeField, offset=133, default=0,
documentation=SweepType.__doc__
)
sweep_trace_taper_length_at_start = field(
NNInt16, offset=135, default=0, documentation=
"Sweep trace taper length at start in milliseconds."
)
sweep_trace_taper_length_at_end = field(
NNInt16, offset=137, default=0, documentation=
"Sweep trace taper length at end in milliseconds."
)
taper_type = field(
TaperTypeField, offset=139, default=0,
documentation=TaperType.__doc__
)
alias_filter_frequency = field(
NNInt16, offset=141, default=0, documentation=
"Alias filter frequency (Hz), if used."
)
alias_filter_slope = field(
Int16, offset=143, default=0, documentation=
"Alias filter slope (dB/octave)."
)
notch_filter_frequency = field(
NNInt16, offset=145, default=0, documentation=
"Notch filter frequency (Hz), if used."
)
notch_filter_slope = field(
Int16, offset=147, default=0, documentation=
"Notch filter slope (dB/octave)."
)
low_cut_frequency = field(
NNInt16, offset=149, default=0, documentation=
"Low-cut frequency (Hz), if used."
)
high_cut_frequency = field(
NNInt16, offset=151, default=0, documentation=
"High-cut frequency (Hz), if used."
)
low_cut_slope = field(
Int16, offset=153, default=0, documentation=
"Low-cut slope (dB/octave)."
)
high_cut_slope = field(
Int16, offset=155, default=0, documentation=
"High-cut slope (dB/octave)."
)
year_recorded = field(
Int16, offset=157, default=0, documentation=
"""Year data recorded. The 1975 standard is unclear as to whether this should
be recorded as a 2-digit or a 4-digit year and both have been used. For
SEG Y revisions beyond rev 0, the year should be recorded as the
complete 4-digit Gregorian calendar year (i.e. the year 2001 should be
recorded as 2001 in base 10 (7D1 in base16))."""
)
day_of_year = field(
DayOfYearField, offset=159, default=0,
documentation=DayOfYearField.__doc__
)
hour_of_day = field(
HourOfDayField, offset=161, default=0,
documentation=HourOfDayField.__doc__
)
minute_of_hour = field(
MinuteOfHourField, offset=163, default=0,
documentation=MinuteOfHourField.__doc__
)
second_of_minute = field(
SecondOfMinute, offset=165, default=0,
documentation=SecondOfMinute.__doc__
)
time_basis_code = field(
TimeBasisCodeField, offset=167, default=0,
documentation=TimeBasisCode.__doc__
)
trace_weighting_factor = field(
NNInt16, offset=169, default=0, documentation=
"Trace weighting factor. Defined as 2**-N volts for the least significant bit. (N = 0, 1, ..., 32767)."
)
geophone_group_num_roll_switch_position_one = field(
Int16, offset=171, default=0, documentation=
"Geophone group number of roll switch position one."
)
geophone_group_num_first_trace_original_field = field(
Int16, offset=173, default=0, documentation=
"Geophone group number of trace number one within original field record."
)
geophone_group_num_last_trace_original_field = field(
Int16, offset=175, default=0, documentation=
"Geophone group number of last trace within original field record."
)
gap_size = field(
NNInt16, offset=177, default=0, documentation=
"Gap size. (Total number of groups dropped)."
)
over_travel = field(
OverTravelField, offset=179, default=0,
documentation=OverTravel.__doc__
)
class TraceHeaderRev1(TraceHeaderRev0, metaclass=FormatMeta):
cdp_x = field(
Int32,
offset=181,
default=0,
documentation="X coordinate of ensemble (CDP) position of this trace. "
"The coordinate reference system should be identified through an extended header Location Data stanza. "
"The xy_scalar field applies to this value.")
cdp_y = field(
Int32,
offset=185,
default=0,
documentation="Y coordinate of ensemble (CDP) position of this trace. "
"The coordinate reference system should be identified through an extended header Location Data stanza. "
"The xy_scalar field applies to this value.")
inline_number = field(
Int32,
offset=189,
default=0,
documentation=
"In-line number for 3-D poststack data. If one in-line per SEG Y file is "
"being recorded, this value should be the same for all traces in the file and the same value will be recorded "
"in bytes 3205-3208 of the Binary File Header." # TODO: replace bytes with field name
)
crossline_number = field(
Int32,
offset=193,
default=0,
documentation=
"Cross-line number for 3-D poststack data. This will typically be the same "
"value as the ensemble (CDP) number in Trace Header ensemble_num field, but this does not have to be the case."
)
shotpoint_number = field(
Int32,
offset=197,
default=0,
documentation=
"Shotpoint number. This is probably only applicable to 2-D poststack data. Note that it is assumed that the "
"shotpoint number refers to the source location nearest to the ensemble (CDP) location for a particular trace. "
"If this is not the case, there should be a comment in the Textual File Header explaining what the shotpoint "
"number actually refers to.")
shotpoint_scalar = field(
Int16,
offset=201,
default=0,
documentation=
"Scalar to be applied to the shotpoint number in trace header field shotpoint_number to give the real value. "
"If positive, scalar is used as a multiplier; if negative as a divisor; if zero the shotpoint number is not "
"scaled (i.e. it is an integer. A typical value will be -10, allowing shotpoint numbers with one decimal digit "
"to the right of the decimal point).")
trace_unit = field(
Int16,
offset=203,
default=0,
documentation="Trace value measurement unit: "
"-1 = Other (should be described in Data Sample Measurement Units Stanza)"
"0 = Unknown, "
"1 = Pascal (Pa), "
"2 = Volts (v), "
"3 = Millivolts (mV), "
"4 = Amperes (A), "
"5 = Meters (m), "
"6 = Meters per second (m/s), "
"7 = Meters per second squared (m/s^2), "
"8 = Newton (N), "
"9 = Watt (W)")
transduction_constant_mantissa = field(
Int32,
offset=205,
default=0,
documentation=
"Transduction Constant mantissa. The mantissa of the multiplicative constant used to convert the Data Trace "
"samples to the Transduction Units (specified in Trace Header transduction_units field)."
"The mantissa of the constant is encoded as a four-byte, two's complement integer. The constant value is given"
"by transduction_constant_mantissa * 10**transduction_constant_exponent."
)
transduction_constant_exponent = field(
Int16,
offset=209,
default=0,
documentation=
"Transduction Constant exponent. The base 10 exponent of the multiplicative constant used to convert the Data "
"Trace samples to the Transduction Units (specified in Trace Header transduction_units field). The constant "
"value is given by transduction_constant_mantissa * 10**transduction_constant_exponent."
)
transduction_units = field(
Int16,
offset=211,
default=0,
documentation=
"Transduction Units. The unit of measurement of the Data Trace samples after they have been multiplied by the "
"Transduction Constant specified in Trace Header fields transduction_constant_mantissa and "
"transduction_constant_exponent. "
"-1 = Other (should be described in Data Sample Measurement Unit stanza), "
"0 = Unknown, "
"1 = Pascal (Pa) ,"
"2 = Volts (v), "
"3 = Millivolts (mV), "
"4 = Amperes (A), "
"5 = Meters (m), "
"6 = Meters per second (m/s), "
"7 = Meters per second squared (m/s2), "
"8 = Newton (N), "
"9 = Watt (W)")
device_trace_identifier = field(
Int16,
offset=213,
default=0,
documentation=
"Device/Trace Identifier — The unit number or id number of the device associated with the Data Trace "
"(i.e. 4368 for vibrator serial number 4368 or 20316 for gun 16 on string 3 on vessel 2). This field allows "
"traces to be associated across trace ensembles independently of the trace number (ensemble_trace_num field)."
)
time_scalar = field(
Int16,
offset=215,
default=0,
documentation=
"Scalar to be applied to times specified in Trace Header fields uphole_time_at_source, uphole_time_at_group,"
"source_static_correction, group_static_correction, total_static, lag_time_a, lag_time_b, "
"delay_recording_time, mute_start_time, mute_end_time to give the true time value in milliseconds. "
"Scalar = 1, +10, +100, +1000, or +10,000. If positive, scalar is used as a multiplier; "
"if negative, scalar is used as divisor. A value of zero is assumed to be a scalar value of 1."
)
source_type = field(
Int16,
offset=217,
default=0,
documentation=
"Source Type/Orientation — Defines the type and the orientation of the energy source. The terms vertical, "
"cross-line and in-line refer to the three axes of an orthogonal coordinate system. The absolute azimuthal "
"orientation of the coordinate system axes can be defined in the Bin Grid Definition Stanza."
"-1 to -n = Other (should be described in Source Type/Orientation stanza), "
"0 = Unknown, "
"1 = Vibratory - Vertical orientation, "
"2 = Vibratory - Cross-line orientation, "
"3 = Vibratory - In-line orientation, "
"4 = Impulsive - Vertical orientation, "
"5 = Impulsive - Cross-line orientation, "
"6 = Impulsive - In-line orientation, "
"7 = Distributed Impulsive - Vertical orientation, "
"8 = Distributed Impulsive - Cross-line orientation, "
"9 = Distributed Impulsive - In-line orientation, ")
source_energy_direction = field(
Int32,
offset=219,
default=0,
documentation= # TODO: This is six bytes. What is the format?
"Source Energy Direction with respect to the source orientation. The positive orientation direction is "
"defined in Bytes 217-218 of the Trace Header. The energy direction is encoded in tenths of degrees "
"(i.e. 347.8° is encoded as 3478).")
source_measurement_mantissa = field(
Int32,
offset=225,
default=0,
documentation=
"Source Measurement mantissa. Describes the source effort used to generate the trace. The measurement can be "
"simple, qualitative measurements such as the total weight of explosive used or the peak air gun pressure or "
"the number of vibrators times the sweep duration. Although these simple measurements are acceptable, it is "
"preferable to use true measurement units of energy or work. The constant is encoded as a four-byte, two's "
"complement integer (source_measurement_mantissa) and a two-byte, two's complement integer "
"source_measurement_exponent) which is the power of ten exponent "
"(i.e. source_measurement_mantissa * 10**source_measurement_exponent)."
)
source_measurement_exponent = field(
Int16,
offset=229,
default=0,
documentation=
"Source Measurement exponent. Describes the source effort used to generate the trace. The measurement can be "
"simple, qualitative measurements such as the total weight of explosive used or the peak air gun pressure or "
"the number of vibrators times the sweep duration. Although these simple measurements are acceptable, it is "
"preferable to use true measurement units of energy or work. The constant is encoded as a four-byte, two's "
"complement integer (source_measurement_mantissa) and a two-byte, two's complement integer "
"source_measurement_exponent) which is the power of ten exponent "
"(i.e. source_measurement_mantissa * 10**source_measurement_exponent)."
)
source_measurement_unit = field(
Int16,
offset=231,
default=0,
documentation=
"Source Measurement Unit. The unit used for the source measurement."
"-1 = Other (should be described in Source Measurement Unit stanza), "
"0 = Unknown, "
"1 = Joule (J), "
"2 = Kilowatt (kW), "
"3 = Pascal (Pa), "
"4 = Bar (Bar), "
"4 = Bar-meter (Bar-m), "
"5 = Newton (N), "
"6 = Kilograms (kg)")
class TraceHeaderRev0(metaclass=FormatMeta):
START_OFFSET_IN_BYTES = 1
LENGTH_IN_BYTES = 240
line_sequence_num = field(
Int32,
offset=1,
default=0,
documentation=
"Trace sequence number within line — Numbers continue to increase if the same line "
"continues across multiple SEG Y files. Highly recommended for all types of data."
)
file_sequence_num = field(
Int32,
offset=5,
default=0,
documentation=
"Trace sequence number within SEG Y file — Each file starts with trace sequence one."
)
field_record_num = field(
Int32,
offset=9,
default=0,
documentation=
"Original field record number. Highly recommended for all types of data."
)
trace_num = field(
Int32,
offset=13,
default=0,
documentation=
"Trace number within the original field record. Highly recommended for all types of data."
)
energy_source_point_num = field(
Int32,
offset=17,
default=0,
documentation=
"Energy source point number — Used when more than one record occurs at the same "
"effective surface location. It is recommended that the new entry defined in Trace "
"Header bytes 197-202 be used for shotpoint number.")
ensemble_num = field(
Int32,
offset=21,
default=0,
documentation="Ensemble number (i.e. CDP , CMP , CRP , etc)")
ensemble_trace_num = field(
Int32,
offset=25,
default=0,
documentation=
"Trace number within the ensemble — Each ensemble starts with trace number one."
)
trace_identification_code = field(
Int16, offset=29, default=0, documentation="Trace identification code")
num_vertically_summed_traces = field(
Int16,
offset=31,
default=1,
documentation=
"Number of vertically summed traces yielding this trace. (1 is one trace, 2 is two summed traces, etc.)"
)
num_horizontally_stacked_traces = field(
Int16,
offset=33,
default=1,
documentation=
"Number of horizontally stacked traces yielding this trace. (1 is one trace, 2 is two stacked traces, etc.)"
)
data_use = field(Int16,
offset=35,
default=1,
documentation="Data use: 1 = Production, 2 = Test")
source_receiver_offset = field(
Int32,
offset=37,
default=0,
documentation=
"Distance from center of the source point to the center of the receiver group (negative if opposite to "
"direction in which line is shot).")
receiver_group_elevation = field(
Int32,
offset=41,
default=0,
documentation=
"Receiver group elevation (all elevations above the Vertical datum are positive and below are negative). The "
"elevation_scalar applies to this value.")
surface_elevation_at_source = field(
Int32,
offset=45,
default=0,
documentation=
"Surface elevation at source. The elevation_scalar applies to this value."
)
source_depth_below_surface = field(
Int32,
offset=49,
default=0,
documentation=
"Source depth below surface (a positive number). The elevation_scalar applies to this value."
)
datum_elevation_at_receiver_group = field(
Int32,
offset=53,
default=0,
documentation=
"Source depth below surface (a positive number). The elevation_scalar applies to this value."
)
datum_elevation_at_source = field(
Int32,
offset=57,
default=0,
documentation=
"Datum elevation at source. The elevation_scalar applies to this value."
)
water_depth_at_source = field(
Int32,
offset=61,
default=0,
documentation=
"Water depth at source. The elevation_scalar applies to this value.")
water_depth_at_group = field(
Int32,
offset=65,
default=0,
documentation=
"Water depth at group. The elevation_scalar applies to this value.")
elevation_scalar = field(
Int16,
offset=69,
default=1,
documentation=
"Scalar to be applied to the elevations and depths specified in: receiver_group_elevation, "
"surface_elevation_at_source, source_depth_below_surface, datum_elevation_at_receiver_group, "
"datum_elevation_at_source, water_depth_at_source and water_depth_at_group, to give the real value. "
"Scalar = 1, +10, +100, +1000, or +10,000. If positive, scalar is used as a multiplier; if negative, scalar is "
"used as a divisor.")
xy_scalar = field(
Int16,
offset=71,
default=1,
documentation=
"Scalar to be applied to all coordinates specified in source_x, source_y, group_x, group_y, cdp_x and cdp_y to "
"give the real value. Scalar = 1, +10, +100, +1000, or +10,000. If positive, scalar is used as a multiplier; "
"if negative, scalar is used as divisor.")
source_x = field(
Int32,
offset=73,
default=0,
documentation=
"Source coordinate - X. The xy_scalar applies to this value. The coordinate reference system should be "
"identified through an extended header Location Data stanza. If the coordinate units are in seconds of arc, "
"decimal degrees or DMS, the X values represent longitude. A positive value designates east of Greenwich "
"Meridian and a negative value designates west.")
source_y = field(
Int32,
offset=77,
default=0,
documentation=
"Source coordinate - Y. The xy_scalar applies to this value. The coordinate reference system should be "
"identified through an extended header Location Data stanza. If the coordinate units are in seconds of arc, "
"decimal degrees or DMS, the Y values represent latitude. A positive value designates north of the equator and "
"a negative value designates south.")
group_x = field(
Int32,
offset=81,
default=0,
documentation=
"Group coordinate - X. The xy_scalar applies to this value. The coordinate reference system should be "
"identified through an extended header Location Data stanza. If the coordinate units are in seconds of arc, "
"decimal degrees or DMS, the X values represent longitude. A positive value designates east of Greenwich "
"Meridian and a negative value designates west.")
group_y = field(
Int32,
offset=85,
default=0,
documentation=
"Source coordinate - Y. The xy_scalar applies to this value. The coordinate reference system should be "
"identified through an extended header Location Data stanza. If the coordinate units are in seconds of arc, "
"decimal degrees or DMS, the Y values represent latitude. A positive value designates north of the equator and "
"a negative value designates south.")
coordinate_units = field(
Int16,
offset=89,
default=0,
documentation=
"Coordinate units: 1 = Length (meters or feet), 2 = Seconds of arc, 3 = Decimal degrees, 4 = Degrees, minutes, "
"seconds (DMS). Note: To encode ±DDDMMSS bytes this value equals ±DDD*104 + MM*102 + SS with xy_scalar set to "
"1; To encode ±DDDMMSS.ss this value equals ±DDD*106 + MM*104 + SS*102 with xy_scalar set to -100."
)
weathering_velocity = field(
Int16,
offset=91,
default=0,
documentation=
"Weathering velocity. (ft/s or m/s as specified in Binary File Header bytes 3255- 3256)" # TODO
)
subweathering_velocity = field(
Int16,
offset=93,
default=0,
documentation=
"Subweathering velocity. (ft/s or m/s as specified in Binary File Header bytes 3255-3256)" # TODO
)
uphole_time_at_source = field(
Int16,
offset=95,
default=0,
documentation=
"Uphole time at source in milliseconds. The time_scalar applies to this value."
)
uphole_time_at_group = field(
Int16,
offset=97,
default=0,
documentation=
"Uphole time at group in milliseconds. The time_scalar applies to this value."
)
source_static_correction = field(
Int16,
offset=99,
default=0,
documentation=
"Source static correction in milliseconds. The time_scalar applies to this value."
)
group_static_correction = field(
Int16,
offset=101,
default=0,
documentation=
"Group static correction in milliseconds. The time_scalar applies to this value."
)
total_static = field(
Int16,
offset=103,
default=0,
documentation=
"Total static applied in milliseconds. (Zero if no static has been applied). "
"The time_scalar applies to this value.")
lag_time_a = field(
Int16,
offset=105,
default=0,
documentation=
"Lag time A. Time in milliseconds between end of 240-byte trace identification header and time break. "
"The value is positive if time break occurs after the end of header; negative if time break occurs before the "
"end of header. Time break is defined as the initiation pulse that may be recorded on an auxiliary trace or as "
"otherwise specified by the recording system. The time_scalar applies to this value."
)
lag_time_b = field(
Int16,
offset=107,
default=0,
documentation=
"Lag Time B. Time in milliseconds between time break and the initiation time of the energy source. May be "
"positive or negative. The time_scalar applies to this value.")
delay_recording_time = field(
Int16,
offset=109,
default=0,
documentation=
"Delay recording time — Time in milliseconds between initiation time of energy source and the time when "
"recording of data samples begins. In SEG Y rev 0 this entry was intended for deep-water work if data "
"recording does not start at zero time. The entry can be negative to accommodate negative start times (i.e. "
"data recorded before time zero, presumably as a result of static application to the data trace). If a "
"non-zero value (negative or positive) is recorded in this entry, a comment to that effect should appear in "
"the Textual File Header. The time_scalar applies to this value.")
mute_start_time = field(
Int16,
offset=111,
default=0,
documentation=
"Mute time — Start time in milliseconds. The time_scalar applies to this value."
)
mute_end_time = field(
Int16,
offset=113,
default=0,
documentation=
"Mute time — End time in milliseconds. The time_scalar applies to this value."
)
num_samples = field(
Int16,
offset=115,
default=0,
documentation=
"Number of samples in this trace. Highly recommended for all types of data."
)
sample_interval = field(
Int16,
offset=117,
default=0,
documentation=
"Sample interval in microseconds (μs) for this trace. The number of bytes in a trace record must be consistent "
"with the number of samples written in the trace header. This is important for all recording media; but it is "
"particularly crucial for the correct processing of SEG Y data in disk files (see Appendix C). "
"If the fixed length trace flag in bytes 3503-3504 of the Binary File Header is set, the sample interval and " #TODO: field names instead of byte offsets
"number of samples in every trace in the SEG Y file must be the same as the values recorded in the Binary File "
"Header. If the fixed length trace flag is not set, the sample interval and number of samples may vary from "
"trace to trace. Highly recommended for all types of data.")
gain_type_of_field_instruments = field(
Int16,
offset=119,
default=0,
documentation=
"Gain type of field instruments. 1 = fixed, 2 = binary, 3 = floating point, 4 ... N = optional use."
)
instrument_gain_constant = field(
Int16,
offset=121,
default=0,
documentation="Instrument gain constant (dB).")
instrument_initial_gain = field(
Int16,
offset=123,
default=0,
documentation="Instrument early or initial gain (dB).")
correlated = field(Int16,
offset=125,
default=1,
documentation="Correlated: 1 = no, 2 = yes.")
sweep_frequency_at_start = field(
Int16,
offset=127,
default=0,
documentation="Sweep frequency at start (Hz).")
sweep_frequency_at_end = field(
Int16,
offset=129,
default=0,
documentation="Sweep frequency at end (Hz).")
sweep_length = field(Int16,
offset=131,
default=0,
documentation="Sweep length in milliseconds.")
sweep_type = field(
Int16,
offset=133,
default=0,
documentation=
"Sweep type: 1 = linear, 2 = parabolic, 3 = exponential 4 = other.")
sweep_trace_taper_length_at_start = field(
Int16,
offset=135,
default=0,
documentation="Sweep trace taper length at start in milliseconds.")
sweep_trace_taper_length_at_end = field(
Int16,
offset=137,
default=0,
documentation="Sweep trace taper length at end in milliseconds.")
taper_type = field(
Int16,
offset=139,
default=0,
documentation="Taper type: 1 = linear, 2 = cos2, 3 = other")
alias_filter_frequency = field(
Int16,
offset=141,
default=0,
documentation="Alias filter frequency (Hz), if used.")
alias_filter_slope = field(Int16,
offset=143,
default=0,
documentation="Alias filter slope (dB/octave).")
notch_filter_frequency = field(
Int16,
offset=145,
default=0,
documentation="Notch filter frequency (Hz), if used.")
notch_filter_slope = field(Int16,
offset=147,
default=0,
documentation="Notch filter slope (dB/octave).")
low_cut_frequency = field(Int16,
offset=149,
default=0,
documentation="Low-cut frequency (Hz), if used.")
high_cut_frequency = field(
Int16,
offset=151,
default=0,
documentation="High-cut frequency (Hz), if used.")
low_cut_slope = field(Int16,
offset=153,
default=0,
documentation="Low-cut slope (dB/octave).")
high_cut_slope = field(Int16,
offset=155,
default=0,
documentation="High-cut slope (dB/octave).")
year_recorded = field(
Int16,
offset=157,
default=0,
documentation=
"Year data recorded. The 1975 standard is unclear as to whether this should be recorded as a 2-digit or a "
"4-digit year and both have been used. For SEG Y revisions beyond rev 0, the year should be recorded as the "
"complete 4-digit Gregorian calendar year (i.e. the year 2001 should be recorded as 2001 in base 10 "
"(7D1 in base16)).")
day_of_year = field(
Int16,
offset=159,
default=0,
documentation="Day of year. (Julian day for GMT and UTC time basis).")
hour_of_day = field(Int16,
offset=161,
default=0,
documentation="Hour of day. (24 hour clock).")
minute_of_hour = field(Int16,
offset=163,
default=0,
documentation="Minute of hour.")
second_of_minute = field(Int16,
offset=165,
default=0,
documentation="Second of minute.")
time_basis_code = field(
Int16,
offset=167,
default=0,
documentation=
"Time basis code. 1 = Local, 2 = GMT (Greenwich Mean Time), 3 = Other, should be explained in a user defined "
"stanza in the Extended Textual File Header, 4 = UTC (Coordinated Universal Time)."
)
trace_weighting_factor = field(
Int16,
offset=169,
default=0,
documentation=
"Trace weighting factor. Defined as 2**-N volts for the least significant bit. (N = 0, 1, ..., 32767)."
)
geophone_group_num_roll_switch_position_one = field(
Int16,
offset=171,
default=0,
documentation="Geophone group number of roll switch position one.")
geophone_group_num_first_trace_original_field = field(
Int16,
offset=173,
default=0,
documentation=
"Geophone group number of trace number one within original field record."
)
geophone_group_num_last_trace_original_field = field(
Int16,
offset=175,
default=0,
documentation=
"Geophone group number of last trace within original field record.")
gap_size = field(
Int16,
offset=177,
default=0,
documentation="Gap size. (Total number of groups dropped).")
over_travel = field(
Int16,
offset=179,
default=0,
documentation=
"Over travel associated with taper at beginning or end of line. 1 = down (or behind) 2 = up (or ahead)"
)
class BinaryReelHeader(metaclass=FormatMeta):
START_OFFSET_IN_BYTES = 3201
LENGTH_IN_BYTES = 400
job_id_num = field(
Int32, offset=3201, default=0, documentation=
"Job identification number")
line_num = field(
Int32, offset=3205, default=0, documentation=
"Line number. For 3-D poststack data, this will typically contain the in-line number."
)
reel_num = field(
Int32, offset=3209, default=0, documentation=
"Reel number."
)
data_traces_per_ensemble = field(
Int16, offset=3213, default=0, documentation=
"Number of data traces per ensemble. Mandatory for prestack data."
)
auxiliary_traces_per_ensemble = field(
Int16, offset=3215, default=0, documentation=
"Number of auxiliary traces per ensemble. Mandatory for prestack data."
)
sample_interval = field(
Int16, offset=3217, default=0, documentation=
"Sample interval in microseconds (μs). Mandatory for all data types."
)
original_field_sample_interval = field(
Int16, offset=3219, default=0, documentation=
"Sample interval in microseconds (μs) of original field recording."
)
num_samples = field(
Int16, offset=3221, default=0, documentation=
"Number of samples per data trace. Mandatory for all types of data. "
"Note: The sample interval and number of samples in the Binary File Header should be for the primary set of "
"seismic data traces in the file."
)
original_field_num_samples = field(
Int16, offset=3223, default=0, documentation=
"Number of samples per data trace for original field recording."
)
data_sample_format = field(
Int16, offset=3225, default=5, documentation=
"Data sample format code. Mandatory for all data. "
"1 = 4-byte IBM floating-point, "
"2 = 4-byte, two's complement integer, "
"3 = 2-byte, two's complement integer, "
"4 = 4-byte fixed-point with gain (obsolete), "
"5 = 4-byte IEEE floating-point, "
"6 = Not currently used, "
"7 = Not currently used, "
"8 = 1-byte, two's complement integer."
)
ensemble_fold = field(
Int16, offset=3227, default=0, documentation=
"Ensemble fold. The expected number of data traces per trace ensemble (e.g. the CMP fold). "
"Highly recommended for all types of data."
)
trace_sorting = field(
Int16, offset=3229, default=0, documentation=
"Trace sorting code (i.e. type of ensemble) : "
"-1 = Other (should be explained in user Extended Textual File Header stanza, "
"0 = Unknown, "
"1 = As recorded (no sorting), "
"2 = CDP ensemble, "
"3 = Single fold continuous profile 4 = Horizontally stacked, "
"5 = Common source point, "
"6 = Common receiver point, "
"7 = Common offset point, "
"8 = Common mid-point, "
"9 = Common conversion point. "
"Highly recommended for all types of data."
)
vertical_sum_code = field(
Int16, offset=3231, default=0, documentation=
"Vertical sum code: "
"1 = no sum, "
"2 = two sum, "
"..., "
"N=M-1 sum (M=2to32,767)."
)
sweep_frequency_at_start = field(
Int16, offset=3233, default=0, documentation=
"Sweep frequency at start (Hz)."
)
sweep_frequency_at_end = field(
Int16, offset=3235, default=0, documentation=
"Sweep frequency at end (Hz)."
)
sweep_length = field(
Int16, offset=3237, default=0, documentation=
"Sweep length in milliseconds."
)
sweep_type = field(
Int16, offset=3239, default=0, documentation=
"Sweep type: 1 = linear, 2 = parabolic, 3 = exponential 4 = other."
)
sweep_trace_number = field(
Int16, offset=3241, default=0, documentation=
"Trace number of sweep channel."
)
sweep_trace_taper_length_at_start = field(
Int16, offset=3243, default=0, documentation=
"Sweep trace taper length at start in milliseconds."
)
sweep_trace_taper_length_at_end = field(
Int16, offset=3245, default=0, documentation=
"Sweep trace taper length at end in milliseconds."
)
taper_type = field(
Int16, offset=3247, default=0, documentation=
"Taper type: 1 = linear, 2 = cos2, 3 = other"
)
correlated_data_traces = field(
Int16, offset=3249, default=0, documentation=
"Correlated data traces: "
"1 = no, "
"2 = yes"
)
binary_gain_recovered = field(
Int16, offset=3251, default=0, documentation=
"Binary gain recovered: "
"1 = no, "
"2 = yes"
)
amplitude_recovery_method = field(
Int16, offset=3253, default=0, documentation=
"Amplitude recovery method: "
"1 = none, "
"2 = spherical divergence, "
"3 = AGC, "
"4 = other"
)
measurement_system = field(
Int16, offset=3255, default=0, documentation=
"Measurement system: Highly recommended for all types of data. "
"If Location Data stanzas are included in the file, this entry must agree with the Location Data stanza. "
"If there is a disagreement, the last Location Data stanza is the controlling authority. "
"1 = Meters, "
"2 = Feet"
)
impulse_signal_polarity = field(
Int16, offset=3257, default=0, documentation=
"Impulse signal polarity : "
"1 = Increase in pressure or upward geophone case movement gives negative number on tape, "
"2 = Increase in pressure or upward geophone case movement gives positive number on tape. "
)
vibratory_polarity_code = field(
Int16, offset=3259, default=0, documentation=
"Vibratory polarity code: "
"Seismic signal lags pilot signal by: "
"1 = 337.5° to 22.5°, "
"2 = 22.5° to 67.5°, "
"3 = 67.5° to 112.5°, "
"4 = 112.5° to 157.5°, "
"5 = 157.5° to 202.5°, "
"6 = 202.5°to 247.5°, "
"7 = 247.5° to 292.5°, "
"8 = 292.5° to 337.5°.")
format_revision_num = field(
Int16, offset=3501, default=0x100, documentation=
"SEG Y Format Revision Number. "
"This is a 16-bit unsigned value with a Q- point between the first and second bytes. "
"Thus for SEG Y Revision 1.0, as defined in this document, this will be recorded as 010016. This field is "
"mandatory for all versions of SEG Y, although a value of zero indicates “traditional” SEG Y conforming to "
"the 1975 standard."
)
fixed_length_trace_flag = field(
Int16, offset=3503, default=0, documentation=
"Fixed length trace flag. A value of one indicates that all traces in this SEG Y file are guaranteed to have "
"the same sample interval and number of samples, as specified in Textual File Header bytes 3217-3218 and "
"3221-3222. A value of zero indicates that the length of the traces in the file may vary and the number of "
"samples in bytes 115-116 of the Trace Header must be examined to determine the actual length of each trace. "
"This field is mandatory for all versions of SEG Y, although a value of zero indicates “traditional” SEG Y "
"conforming to the 1975 standard."
)
num_extended_textual_headers = field(
Int16, offset=3505, default=0, documentation=
"Number of 3200-byte, Extended Textual File Header records following the Binary Header. "
"A value of zero indicates there are no Extended Textual File Header records (i.e. this file has no Extended "
"Textual File Header(s)). A value of -1 indicates that there are a variable number of Extended Textual File "
"Header records and the end of the Extended Textual File Header is denoted by an ((SEG: EndText)) stanza in "
"the final record. A positive value indicates that there are exactly that many Extended Textual File Header "
"records. Note that, although the exact number of Extended Textual File Header records may be a useful piece "
"of information, it will not always be known at the time the Binary Header is written and it is not mandatory "
"that a positive value be recorded here. This field is mandatory for all versions of SEG Y, although a value "
"of zero indicates “traditional” SEG Y conforming to the 1975 standard."
)
class BijectiveHeader(Header):
field_a = field(Int32, 1, 0, "Field A.")
field_b = field(NNInt32, 5, 0, "Field B.")
class CoincidentFieldsWithDifferentTypesHeader(Header):
field_a = field(Int32, 1, 0, "Field A.")
field_b = field(NNInt32, 1, 0, "Field B.")
class OverlappingFieldsHeader(Header):
field_a = field(Int32, 1, 0, "Field A.")
field_b = field(Int32, 3, 0, "Field B.")
class ShortHeader(Header):
START_OFFSET_IN_BYTES = 1
LENGTH_IN_BYTES = 3
field_a = field(Int32, 1, 0, "Field A.")
class MyHeader(Header):
START_OFFSET_IN_BYTES = 1
field_a = field(Int32, 1, 0, "Field A.")
field_b = field(NNInt32, 5, 0, "Field B.")
field_c = field(Int32, 1, 0, "Field C.")
class BijectiveHeader(Header):
START_OFFSET_IN_BYTES = 1
field_a = field(Int32, 1, 0, "Field A.")
field_b = field(NNInt32, 5, 0, "Field B.")
