SAGE Facility MUSTANG metrics Web Service Documentation

num_overlaps Number of data overlaps in a day

Summary

This metric reports the number of overlaps encountered in a 24-hour window.

Uses

Data in the IRIS SEED archive is currently merged (M-quality) data, which by definition omits overlapping data. Consequently, this metric is deprecated.

Data Analyzed

Traces – one N.S.L.C (Network.Station.Location.Channel) per measurement
Window – 24 hours starting at 00:00:00 UTC
Data Source – IRIS SEED archive

SEED Channel Types – ?H?, ?L?, ?N?, ?G?, ?P?, VM? | High Gain, Low Gain, Accelerometer, Gravimeter, Geophone, Mass Channels

Algorithm

  • Request 24 hours of data for a single Channel (N.S.L.C).
  • Request the data sample rate, defining an overlap as larger than one sample interval.
  • For x data segments returned,
    • Calculate end time of each data segment returned for that day:
      endtime(x) := starttime(x) + ( (num_samples(x) – 1) / sample_rate)
    • Calculate overlap lengths between segments:
      overlap(x) := endtime(x-1) – starttime(x)  - (1 / sample_rate)
    • Count the number of overlaps for the segments – if the beginning of one data segment starts on or before the end of the next, it is an overlap:
      num_overlaps = count(overlaps(x) < 0)

Metric Values Returned

value – daily number of overlaps
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 – date/time the measurement was made and loaded into the MUSTANG database (UTC)

Notes

Overlaps are currently not measured across day boundaries. An overlap crossing a day boundary is treated as two separate overlaps for purposes of counting overlaps.

Contact

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