SAGE Facility MUSTANG metrics Web Service Documentation

This metric reports the total number of gaps encountered within the requested time period, calculated at query time. It calculates gaps in data availability based on information stored in the rapidly-accessible IRIS SEED and PH5 archive database indexes (ts_index), as returned by the service.iris.edu/fdsnws/availability or service.iris.edu/ph5ws/availability web service.

The ts_num_gaps_total metric is currently a prototype that will eventually become a standard MUSTANG metric.

Data gaps can indicate problems with data transmission configuration or performance, power cycling or other equipment down time, or data loss after transmission. The metric can also be used to cull data that is not continuous enough for certain research applications.

Traces – one N.S.L.C (Network.Station.Location.Channel) per measurement
Window – from start time to the end time of the request
Data Source – IRIS miniSEED archive database time series index (ts_index)

SEED Channel Types – All Time Series Channels

• Request availability web service trace extents for the time duration on each matching N.S.L.C.
  

  total_duration = request_end_time - request_start_time;
  

• For x entries/data segments returned,
  • Calculate time between segments:
    

    segdt(x) = endtime(x-1) – starttime(x)
    

  • Increment count if a gap is found:
    

    if ( segdt(x) > (1.5 / sample_rate) )
        total_gaps = total_gaps + 1;
    else
        skip;
    

value – gap count
target – the trace analyzed, labeled as N.S.L.C.Q (Network.Station.Location.Channel.Quality)
start – beginning of the date requested (UTC)
end – end of the date requested (UTC)
lddate – UTC date/time the measurement was made

If the user specified end date does not include hour:min:sec, then it defaults to 00:00:00.

• Robert Casey