SAGE Facility MUSTANG metrics Web Service Documentation

This metric reports the total length of time in seconds of all data gaps encountered within a 24-hour window, 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 and service.iris.edu/ph5ws/availability web services.

The ts_gap_length 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 – 24 hours starting at 00:00:00 UTC
Data Source – IRIS miniSEED archive database time series index (ts_index)

SEED Channel Types – All Time Series Channels

• Assemble availability web service trace extents for 24 hours on each matching N.S.L.C.
• For k data segments returned,
  • Calculate gap lengths between segments:
    

    gap(k) = start[k+1] - end[k] - (1 / sample_rate[k]);
    

  • Sum the gap values greater than zero – if the beginning of one data segment lags the day boundary or previous segment’s end time by more than one sample interval, it is a gap:
    

    ts_gap_length = sum(gap(k) > 0)
    

value – total gap length expressed in seconds
target – the trace analyzed, labeled as N.S.L.C.Q (Network.Station.Location.Channel.Quality)
start – beginning of the data day requested (00:00:00 UTC)
end – end of the data day requested (truncated as 23:59:59 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.

If the requested start time is earlier than the metadata start time for the station-channel, the first 24-hour day returned will be 00:00:00-23:59:59 UTC for the day the metadata begins.

If the requested end time is later than the metadata end time for the station-channel, the last 24-hour day returned will be 00:00:00-23:59:59 UTC for the day the metadata ends.

• Robert Casey