has been implemented using the standard as defined by SEG [1]
also has support for reading and writing the format used by CWP's Seismic Unix package (the SU format), which is merely a simplified version the format.
A short description of the formats follows here
A file consists of a 3600 byte header; a number of extended textual headers; a number trace headers+data.
A 3200 byte Textual File Header, ASCII or EBCDIC formated.
A 400 byte Binary File Header
A (optional) number of 'Extended Textual File Headers', 3200 bytes long, ASCII or EBCDIC formatted.
A number of traces, separated into a 240 bytes long binary Trace Header, followed by the Trace Data, that can be formatted in a number of ways : IEEE, IBM Floating Point, 1,2 and 4 byte two's complement integers.
A SU formatted file is just a simple version of a file, containing only trace information :
No 3200 byte textual header and no extended textual headers.
No binary header.
The data must be formatted as IEEE.
Data can be both little and big endian formatted.
As of version supports the following parts of the revision 0 and 1.
The Textual 400 byte file header can be both ASCII and EBCDIC formatted, using revision 1.
Both ASCII and EBCDIC are supported since version 0.39.
In revision 1 a number of extended textual file headers are allowed.
As of version 0.9 extended textual headers are supported by .
The following data formats are supported :
Table 1. Supported revision 0 (1975)
| Type | DataSampleFormat | Supported |
|---|---|---|
| 1 | 4 Byte IBM Floating Point | Yes |
| 2 | 4 Byte Fixed Point | No |
| 3 | 2 Byte Fixed Point | No |
| 4 | 4 Byte Fixed Point with Gain | No |
Table 2. Supported revision 1 (2002)
| Type | DataSampleFormat | Supported |
|---|---|---|
| 1 | 4 Byte IBM Floating Point | Yes |
| 2 | 4 Byte two's complement integer | Yes |
| 3 | 2 Byte two's complement integer | Yes |
| 4 | 4 Byte Fixed Point with Gain | No |
| 5 | 4 Byte IEEE FLoating Pint | Yes |
| 6 | Not Specified | |
| 7 | Not Specified | |
| 8 | 1 Byte Fixed Point with Gain | Yes |
The type number is the number that should be used as 'dsf' (Data Sample Format), for functions like
ReadSegy.m,
WriteSegy.m,
WriteSegyStructure.m.
| © 2004-2006 Thomas Mejer Hansen. | This site is hosted by
|