1. Rune Hagelund, WesternGeco Stewart A. Levin, Halliburton
SEGD rev 3.0 proposal
Rune Hagelund, WesternGeco
Stewart A. Levin, Halliburton

2. Overview of rev 3.0 proposal
All features discussed at SEG New Orleans have been implemented
With a few additions
SEGD Tape Label, General Header 1 and Demux Trace Header left as is (with a few exceptions)
Be an efficient format for transferring information between acquisition and QC/processing
SEGD is not a processing format
More space for user-defined header blocks

3. Overview of rev 3.0 proposal
Increased flexibility
Header blocks tagged to allow shot specific (attached to general header) or trace specific information
Flexible samplerates, header sizes, reclength etc.
Increased robustness
Tagged header blocks
Size of shot/data in General Header
Simplified encoding/decoding
No complex datatypes, using 4byte float, int etc
Explicit values (ex. #samples/trace)‏
No dependencies between header blocks
Additional functionality

4. New functionality in rev 3.0
Positions can be tagged to all traces/equipment
Multiple positions (in space and time)‏
Format TBD by pos group
Support for multi-component data
Node number, trace grouping, orientation header
New General Trailer format
Flexible, allows any data-block to be appended
Standardized edits can be appended to General Trailer
Allows easy addition of edits post-acquisition
8068: IEEE 8 byte samples

5. New functionality in rev 3.0
Supporting complex shooting schemes
Multiple source efforts per shot record
Multiple sources firing simultaneously
Supporting complex source configurations
Traces and measurements for sources and parts of sources
Align SEGD with SPS

6. New functionality in rev 3.0
All measurements now properly tagged with accurate, absolute timestamp (if available)‏
Positions, traces, shot, etc.
All header sizes extended
More room for acquisition system defined blocks
Existing trace ext hdr blocks may be used....
...but remember to use correct block tag
Standardizing storage of SEGD
One header block spanning multiple tape blocks
A trace spanning multiple tape blocks
Fixed/variable block devices
Disk storage
Transfer across network

7. New functionality in rev 3.0
Standardizing storage of common survey information
Vessel/crew identification
Survey area name
Client identification
Job identification
Line identification (Record set identification)‏
Size of record, data, and header explicit in General Header

8. New functionality in rev 3.0
Logical numbering of traces/source points extended to handle all operation types
Line number
Point number
Point index
Group index
Depth index
Reshoot index

9. New functionality in rev 3.0
More sensor types/channel types explicitly supported
Wind, depth, reference signals, source measurements etc.
Sensor sensitivity value stored per channel
Convert to actual physical unit
Support non-voltage measurements

10. New functionality in rev 3.0
Table Of Contents file
Stored at end (or beginning) of tape
Lists all SEGD records on a tape
Enable fast access to data
May be stored on disk (to simplify data mgt)‏

11. New functionality in rev 3.0
Line number -> Record set number
To be usable for all types of operation
Only 3 General Header blocks required in rev 3
Everything else optional

12. Header sizes Channelset header block 96 bytes Header block sizes
General header blocks (2 MB)‏
Channelset header – blocks (~6MB)
Skew blocks – blocks (~2MB)‏
Extended header – blocks (~512MB)‏
External header blocks (~512MB)‏
Trace Header Extension – 255 blocks (8160 bytes)‏
General Trailer – blocks (~128GB)‏

13. Samplerate / timestamp
Sample rates steps of 1 microsecs
No longer a base scan rate
Dominant Sample interval used for backwards compatibility
Timestamp – counting microsecs since 6 jan 1980 (GPS epoch)‏
8 byte integer
Negative timestamps allowed
years range

14. Trace size Traces can be 2147 secs long Negative start times allowed
Extended recording mode allows up to secs (1628 days) of data to be stored in one record

15. Filters Extended filter definitions
Frequencies and slopes are IEEE floats (4 bytes)
Filter type
Filter delay