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15. Radiolocation Sounding Data Format
“
Prism2
” software uses International Geophysical Data Format the by the Society
of Exploration Geophysicists (SEG-Y).
15.1 SEG-Y Sounding Data Format
File begins from a 3200-byte EBCDIC descriptive reel header record which contains
service information. Following EBCDIC there is a 400-byte binary reel header record
containing service information about the data:
Offset
from file
beginning
Parameter
length,
Bytes
Parameter
record
format
Comments
3200
4
int
Job identification number
3204
4
int
Line number
3208
4
int
Reel number
3212
2
short int
Number of data traces per record
3214
2
short int
Number of auxiliary traces per record
3216
2
short int
Sample interval of this reel's data in
PICOseconds
3220
2
short int
Number of samples per trace for this reel's
data
3222
2
–
Unused
3224
2
short int
Data sample format code:
1 = 32-bit IBM floating point;
2 = 32-bit fixed-point (integer);
3 = 16-bit fixed-point (integer);
4 = 16-bit fixed-point with gain code
(integer).
3226
2
short int
CDP fold (expected number of data traces
per ensemble)
3228
26
–
Unused
3254
2
short int
Measuring system:
1 = meters;
2 = feet.
3256
344
–
Unused
Then there goes trace records, each contains a 240-byte binary trace header and trace
data. Offset from the beginning of a file to the K
th
trace record is 3600+K*(240+S*2),
where S – number of samples in a trace, and K – trace number (counted from the zero trace
and not from the first one). Trace data recorded sample by sample. No separators or
symbols are used between samples. Each sample is represented as the data sample format
code from binary reel header and takes (2 or 4)*N Bytes. Note, that samples and traces are
