Ingenieria

SEG Y rrev 1 Data Exchange format[1]



SEG Technical Standards Committee[2]



Draft 8.2Release 1.0, May 2002
Content

1. Introduction 1


2. Summary 1

2.1. Unchanged Items 1
2.2. Changes from rev 0 to rev 1 1
2.3. Notation 1
2.4. Controlling Organization 1
2.5. Acknowledgments 1

3. SEG Y File Structure 2

3.1. Recording Medium 2
3.2. File Structure 33.3. Number Formats 3
3.4. Varying Trace Lengths 3
3.5. Coordinates 4

4. Textual File Header 4


5. Binary File Header 6


6. Extended Textual File Header 9

6.1. Structure of Extended Textual Header 10
6.2. EndText stanza 11
6.3. Stanza Example 11

7. Data Traces 12

7.1. Trace Header 12
7.2. Trace Data 20

Appendix A. Writing SEG Y Data to a Disk File 20Appendix B. SEG Y Tape Labels 21


Appendix C. Blocking of SEG Y Files on Tape 23


Appendix D. Extended Textual Stanzas 24

D-1. Location Data 24
D-1.1 Stanza for Location Data 24
D-1.2 Example Stanza for Location Data 26
D-2. Bin Grid Definition 27
D-2.1 Stanza for Bin Grid Definition 27
D-2.2 Example for Bin Grid Definition 30
D-3. Data Geographic Extent &Coverage Perimeter 31
D-3.1 Stanza for Data Geographic Extent 33
D-3.2 Example for Data Geographic Extent 33
D-3.3 Stanza for Coverage Perimeter 34
D-3.4 Example Stanza for Coverage Perimeter 35
This example is based on Figure 3. 35
D-4. Data Sample Measurement Unit 36
D-4.1 Stanza for Data Sample Measurement Unit 36
D-4.2 Example stanza for Data Sample Measurement Unit 36D-5. Processing History 37
D-5.1 Stanza for Processing History 37
D-5.2 Example stanza for Processing History 37
D-6. Source Type/Orientation 38
D-6.1 Stanza for Source Type/Orientation 38
D-6.2 Example stanza for Source Type/Orientation 38
D-7. Source Measurement Unit 39
D-7.1 Stanza for Source Measurement Unit 39
D-7.2 Example stanza for Source Measurement Unit39

Appendix E. Data Word Format 39


Appendix F. EBCDIC and ASCII Codes 42


Appendix G. References 45



Figures
Figure 1 Byte stream structure of a SEGY file with N Extended Textual File Header records and M traces records 2
Figure 2 Bin grid definition 28
Figure 3 Various data extents and coverage perimeters for a seismic survey 32


Tables
Table 1 Textual File Header 5Table 2 Binary File Header 6
Table 3 Trace Header 12
Table 4 SEG Y Tape Label 21
Table 5 Stanza for Location Data 24
Table 6 Stanza for Bin Grid Definition 28
Table 7 Stanza for Data Geographic Extent 33
Table 8 Stanza for Coverage Perimeter 34
Table 9 Stanza for Data Sample Measurement Unit 36
Table 10 Stanza for Processing History 37
Table 11 Stanza for Source Type/Orientation 38
Table12 Stanza for Source Measurement Unit 39
Table 13 IBM 3270 Char Set Ref Ch 10, GA27-2837-9, April 1987 42

Introduction

Since the original SEG Y Data Exchange Format (revision 0, reference page 45) was published in 1975 it has achieved widespread usage within the geophysical industry. This widespread usage has brought about many proprietary variations. Since the publication of SEG Y rev0, the nature of seismic data acquisition, processing and seismic hardware has changed significantly. The introduction of 3-D acquisition techniques and high speed, high capacity recording media dictate the need for revisions to the SEG Y rev 0 format. The major changes introduced by SEG Y rev 1 are: standardizing the location of header information needed for current processing practices anddefining a SEG Y data set as a byte stream format. The SEG Technical Standards Committee strongly encourages producers and users of SEG Y data sets to move to the revised standard in an expeditious fashion.

Summary


1 Unchanged Items

• EBCDIC encoding is allowed for text.
• The size of the original 3200-byte Textual File Header, 400-byte Binary File Header and 240-byte Trace...