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Waveform data will represent the largest type of request processing in the NetDC system. The files created will generally be quite large in size and processing times can take hours or days in duration, depending on the scope of the user request and the speed of each data center's waveform processing system. Despite all this, waveform data represents the core piece of information for users interested in seismic data and NetDC has been designed around having such requests fulfilled.

Unlike inventory requests, waveform requests cannot be requested with variable number of fields filled in. All fields must be included in a ".DATA" request line, including the start and end time, in order for the request line to be accepted.

A sample data request line is shown here for illustration:

.DATA * II BFO * BHZ "1998 02 03 04 20 34" "1998 03 04 20 20 00"

A request for waveform data will take considerably longer to process than requests for inventory and response data. If the user has mixed inventory or response request lines with waveform request lines the inventory and response data will generally be returned sooner than waveform data. NetDC cannot control or estimate how long processing for a request will take.

The default format for waveform data is binary SEED format. Because it is binary data, it is not feasible to email the shipment to the user (not everyone can read mail attachments), so the default form of shipment is "FTP". Another issue is merging of data. SEED products produced at different data centers are collected at the hub site and need to be concatenated into a single output file. However it is difficult to separate out the individual SEED volumes from a single file when they have simply been appended to one another. The solution currently implemented to get around this problem is to ship the waveform data as a UNIX "tar" archive, which will consist of individual SEED volumes produced at each data center.

Fig 8.1 - With three separate SEED volumes, it is preferable to package them into a "tar" file rather than append the three volumes together

If any information is needed on the particulars of SEED volumes, please contact the IRIS Data Management Center or consult our web site at http://www.iris.washington.edu.

introduction •• overall concept •• request format •• request reception and delegation
datagrams •• local request processing •• inventory requests •• response requests
waveform requests •• product shipment •• installation and setup •• writing interface code
troubleshooting •• future implementations •• conclusion •• appendix A - summary of NetDC datagrams

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