VANGUARD - Dual files per shot

Vanguard is a method to transfer files from seismic field tapes to CD or DVD. It takes all the records from tape and splits them up into a header file and a record file. Here's why we don't like it:

1. Does not represent a single format. Formats have to be defined for each new format. Formats defined so far for SEGA through SEGD. To identify the header/data pairs they usually contain a common prefix, 'FILE' or just 'F' and a suffix that separates the header and data portion. For example an extension of '.hb' and '.sb' for SEGB data. Notice that the selection of letters is critical; the header record has to sort before the data record. There is no limit to the number of formats that Vanguard represents.

2. Proper data identification, if the data that is archived in Vanguard is not properly identified and the file ID’s are not properly translated to the Vanguard file names then the data is useless.

3. How does Vanguard store a dataset where the line is shot backwards?? Vanguard does not preserve the order of the data in the format.

4. Provision for future data considerations, because Vanguard requires a new Vanguard data definition for every seismic format. If a new format evolved in the industry then a new Vanguard standard would also have to be created. The Vanguard format has no provision for future changes in respect to the storage formats used to acquire seismic.

5. No check sum information. There is nothing in the Vanguard format to ensure that the data is identical to the data read of the original media.

6.  A single 200 shot line would result in 400 files that need to be managed. These could easily be managed in a single ENCAP file set. The result of putting the file into Vanguard format would be this, a single 200 shot survey would breaks it into 400 files that need to be managed. In the case of marine data or large surveys this is not feasible and is not very manageable.

7. Duplicate field file numbers or repeated field files can not be accommodated for in Vanguard.

8. File based format that concatenates data records or traces to create a single file, in trace sequential SEGD they would have one file for the header and one file for all the trace records. The problem that often exists is that if you have one bad trace record, corruption of the entire file many occur. This problem would be common in the archiving of Segy tapes using Vanguard as an output format.

Processing shops generally like to work with Vanguard. Our encapsulation method provides all the advantages of a proper archive while preserving all the benefits of Vanguard. Note that our examples below have archived vanguard files. We have even preserved the directory paths. (Paths lacking data have been deleted). You can even use our viewer to verify the field file numbers.