|Observatories and Research Facilities for EUropean Seismology|
|Volume 1, no 2||April 1999||Orfeus Newsletter|
FDSN WG on data exchange: Meeting December 4, 1998, Seattle, USAReporter chairman Bernard Dost
A proposal was tabled for the post archiving of timing corrections, enabling a correction to (mini)SEED data records in a mass storage system. The change requires only the use of one previously unused bit in the data header, so the impact is assumed to be minimal. Again, since the proposal was coming in at the meeting, members were solicited to give their comments by email before January 15, 1999. No response was received at this date, so the proposal is accepted. (link to the email document is pending)
Until now the Network Codes (NCs), which are provided by IRIS, are only using upper case characters. There was a concern that network codes could run out and it was proposed to also include lower case characters. Tim Ahern reported that he would strongly discourage the use of case sensitive NCs and he offered to review the concern on the limits on the NCs.
In the conversion from GSE 2.X data to SEED the original instrument response may be defined in the form of frequency-amplitude-phase (FAP) numbers. In SEED poles and zeroes are required. The question was raised if SEED could also accept only FAP information. Bernard Dost strongly argued against this, since users will have to make their own adaptation to poles and zeroes if they want to correct for instrument response, initiating a multitude of responses for the same instrumentation. Also, there is a tendency to process large data volumes in an automatic fashion and the conversion from FAP to poles and zeroes can not easily be automated.
A brief discussion started on additions and/or changes in the SEED format needed to incorporate strong motion data in SEED. One problem is the channel naming convention and it was proposed to use an unused letter. No definite conclusion was reached, but the issue is open for discussion.
Tim Ahern will check the use of orientation code for electromagnetic recording in SEED. He also encourages people to look at the electronic version of the SEED manual, since changes, like proposed at this meeting, will be available only in the electronic version for quite some time.
The continuous FDSN archive is collecting most data routinely,
but there are a few important issues. First of all, MedNet sent its
data until November 1995 and has a considerable delay. It was not known
in detail if data from stations, which do not belong to a major network, do
come in regularly and if there are any issues. The Australian data may
be a problem, as well as the Mexican FDSN stations.
Tim Ahern prepared a handout concerning FARM volume production by FDSN members. (link document is pending).
It was suggested to start thinking about moving from CD-ROMs to DVDs in the near future. The good thing is the increase in data storage. The bad news is the absence of a real standard for data storage at DVD. In summer 1999 new developments are expected that may bring the use of this technology closer.
The understanding was that VSAT is a point to point protocol and that multicast is not yet developed. One should keep an open eye on developments in this field.
Genevieve Roult argued to cut the response plots in the station book at the Nyquist frequency. This was accepted.
The question was raised if the FDSN should consider to use CD-1 or
CD-2 as a continuous format. It was decided that the format should
be evaluated and comments discussed in the next WG meeting.