Table 4

Entries in the PASSCAL SEG-Y trace headers; range of byte numbers in header is given for each entry. This PASSCAL header format is a modified version of the standard SEG-Y format and the entries marked with an asterisk are header values not specified in the standard SEG-Y format.


Byte Numbers
Description

1-4
5-8
9-12
13-16
|
29-30
|
69-70
71-72
|
89-90
|
103-104
|
115-116

117-118

119-120
121-122
|
157-158
159-160
161-162
163-164
165-166
167-168
|
181-186*
187-194*
195-198*
199-200*
201-204*
205-206*
207-208*
209-210*
211-212*
213-214*
215-216*
217-218*
219-220*
221-224*

225-226*
|
229-232*
233-236*
237-240*

Trace sequence number within data stream
Trace sequence number within reel (same as above)
Event number
Channel number

Trace identification code (= 1 for seismic data)

Elevation scale constant (= 1)
Coordinate scale constant (= 1)

Coordinate units (= 2 for latitude/longitude)

Low 2 bytes of the total shift in milliseconds

Number of samples in this trace (note if equal to 32767 see bytes 229-232)
Sample interval in microsecs for this trace (note if equal to 1 see bytes 201-204)
Fixed gain flag (= 1)
Gain of amplifier

Year data recorded
Day of year
Hour of day (24 hour clock)
Minute of hour
Second of minute
Time basis code (1 = local; 2 = GMT; 3 = other)

Station name code (5 chars + 1 for termination)
Sensor serial code (7 chars + 1 for termination)
Channel name code (3 chars + 1 for termination)
High 2 bytes of the total shift in milliseconds
Sample interval in microsecs as a 32 -bit integer
Data format flag (0 = 16-bit interger; 1 = 32-bit integer)
Milliseconds of second for first sample
Trigger time year
Trigger time julian day
Trigger time hour
Trigger time minutes
Trigger time seconds
Trigger time milliseconds
Scale factor (IEEE 32 -bit float);
true amplitude = (data value)*(scale factor)/gain
Instrument serial number

Number of samples as a 32-bit integer
Max value in counts
Min value in counts