The following tables show SIA header names and byte/format assignments for the standard SEGY binary reel and trace headers, and also two extensions of trace header format used in PASSCAL and Seismic UNIX files.
Data sample format is normally controlled by the corresponding value of the reel header.
Input and output in SEGY format is performed by modules readbf and write, respectively.
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Name in SIA | First byte | Length | Format in file | Format in SIA | Description |
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Coordinate scalar for the following coordinates |
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Shot X coordinate |
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Shot Y coordinate |
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Receiver X coordinate |
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Receiver Y coordinate |
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Record start - year |
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Record start - day |
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Record start - hour |
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Record start - minute |
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Record start - second |
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This SEGY trace header format extension is used in PASSCAL programs, such as ref2segy, segygather, or txn2segy. Like Seismic UNIX, PASSCAL SEGY does not use reel header.
Name in SIA | First byte | Length | Format in file | Format in SIA | Description |
station | 181 | 6 | CHARACTER | CHARACTER | Station name |
sensor | 187 | 8 | CHARACTER | CHARACTER | Sensor type |
channel | 195 | 4 | CHARACTER | CHARACTER | Channel name |
static | 199 | 2 | INTEGER | REAL | Record time start - msec |
sampin2 | 201 | 4 | INTEGER | REAL | Sample interval |
datafrm | 205 | 2 | INTEGER | INTEGER | Data format |
msec | 207 | 2 | INTEGER | INTEGER | Record start - millisecond |
e_year | 209 | 2 | INTEGER | INTEGER | Event year |
e_day | 211 | 2 | INTEGER | INTEGER | Event day |
e_hour | 213 | 2 | INTEGER | INTEGER | Event hour |
e_min | 215 | 2 | INTEGER | INTEGER | Event miniute |
e_sec | 217 | 2 | INTEGER | INTEGER | Event second |
e_msec | 219 | 2 | INTEGER | INTEGER | Event millisecond |
gain | 221 | 4 | REAL | REAL | |
inst_no | 225 | 2 | INTEGER | INTEGER | Number of the instrument |
filter | 227 | 2 | INTEGER | INTEGER | |
nsampt2 | 229 | 4 | INTEGER | INTEGER | Number of samples |
maxsamp | 233 | 4 | INTEGER | REAL | |
minsamp | 237 | 4 | INTEGER | REAL |
SEGY trace header parameters used by Seismic UNIX programs.
Name in SIA | FIrst byte | Length | Format in file | Format in SIA | Description |
su.d1 | 181 | 4 | REAL | REAL | Sample spacing for non-seismic data |
su.f1 | 185 | 4 | REAL | REAL | First sample location for non-seismic data |
su.d2 | 189 | 4 | REAL | REAL | Sample spacing between traces |
su.f2 | 193 | 4 | REAL | REAL | First trace location |
su.ungp | 197 | 4 | REAL | REAL | Negative of power used for dynamic range compression |
su.unsc | 201 | 4 | REAL | REAL | Reciprocal of scaling factor to normalize range |
su.ntr | 205 | 4 | INTEGER | INTEGER | Number of traces |
su.mark | 209 | 2 | INTEGER | INTEGER | Mark selected traces |