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SEG-Y files produced from PH5 data sets


The SEG-Y file written by ph5toseg is in big endian byte order and attempts to follow the SEG-Y rev 1 standard (May 2002) as outlined in the table below.

The file does not contain a Tape Label.

Textural File Header
Byte Number Field Description
1-3200 single header written as ASCII, as opposed to EBCDIC, with no extensions
Binary File Header
3201-3204 Job Identification Number: left blank.
3205-3208 Line Number: set to the array name, 1, 2, 3, etc.
3209-3212 Reel Number: set to 1.
3213-3214    Traces Per Ensemble: set to the number of traces in the gather.
3215-3216 not used.
3217-3218 Sample Interval: set to the sample interval in micro-seconds. All traces have the same sample interval.
3219-3220 not used.
3221-3222 Number of Samples Per Trace: set to the number of samples per trace.  All traces in the gather have the same number of samples. The maximum allowed is 32767 samples.
3223-3224 Field Samples Per Trace: set the same as the Number of Samples Per Trace.
3225-3226 Data Format: set to 5 (4-byte IEEE floats).
3227-3254 not used.
3255-3256 Measurement System: set to 1 (meters).
3257-3500 not used.
3501-3502 SEG-Y Revision Number: set to 0x0100 (rev 1.0).
3503-3504 Trace Length Flag: set to 1 (all traces the same length).
3505-3506 Number of Extended Text Headers: set to 0
  All unused fields in the binary file header are set to 0x00.
Trace Header
1-4 Line Trace Sequence Number: set to 1.
5-8 not used.
9-12 Field Record Number: set to the recording window number.
13-16 Field Trace Number: set to the sequence number of the trace in the gather.
17-20 Energy Source Point Number: set to the event ID.
21-28 not used.
29-30 Trace ID Code: set to 15 for the Z component, 16 for the N component, or 17 for the E component. If unknown it is set to 1 for seismic data.
31-36 not used.
37-40 Source to Receiver Distance: set to the distance from the source to the receiver in meters. The source to receiver distance sign is determined by calculating the least-squares linear regression of receiver locations of the array and the intersection of a line perpendicular to the linear regression which crosses through the shot location.  Receiver locations to the left of this intersection have negative source to receiver distances.
41-44 Receiver Group Elevation: set to the integer value of the station elevation in decimeters.
45-48 Source Elevation: set to the surface elevation of the source in decimeters.
49-52 Source Depth: the distance from the surface to the source in decimeters.
53-68 not used.
69-70 Elevation and Depth Scaler: set to -10, (divide by 10 to get meters).
71-72 Coordinate Scaler: set to -10,000, (divide by 10,000 to get degrees).
73-76, 77-80 X and Y Coordinates, respectively, of the source are set to the longitude and latitude in degrees multiplied by 10,000. Set to 0 if unknown.
81-84, 85-88 X and Y Coordinates, respectively, of the receiver are set to longitude and             latitude in degrees multiplied by 10,000. Set to 0 if unknown.
89-90 Coordinate Units: set to 3, (decimal degrees).
91-114 not used.
115-116 Number of Samples: set to the number of samples in the trace.
117-118 Sample Interval: set to the sample interval of the data in micro-seconds.
119-120 Gain Type: set to 1 (fixed).
121-122 Gain Constant: set to the gain set in the data logger.
157-158, 159-160 Year and Day of Year, respectively of the trace start time.

161-162, 163-164, 165-166

Hour, Minute and Seconds, respectively of the trace start time.
167-168 Time Basis Code: set to 4 (UTC).
169-170 Trace Weighting Factor: ln (bit_weight_in_volts) / ln (2).
171-172 Geophone Group Number: set to the array ID.
173-206 not used.
207-208 Milli-seconds are set in the extended part of the header (non-standard).
  All unused fields in the trace header are set to 0x00.