SAGE Facility MUSTANG metrics Web Service Documentation

Reports the daily average of timing quality values stored in SEED Blockette 1001. Not all miniSEED data contain Blockette 1001.

Depending on how dataloggers and software quantify timing quality in the SEED Blockette 1001, average timing quality reflects the accuracy of a datalogger’s sampling clock relative to an external reference such as a GPS clock. Although SEED timing quality values vary among dataloggers and institutions, they typically indicate whether an external GPS reference was available, when the GPS clock last achieved a satellite lock and whether the GPS and sampling clocks achieved a phase-locked loop. Because the timing_quality metric produces an average, stations with GPS clocks that run continuously will generally have a higher average quality than those with a power-cycled GPS and comparable locking behavior.

Poor timing quality does not necessarily imply that the datalogger time stamp clock has drifted noticeably. There is also no relationship between timing quality and whether or not timing corrections have been applied.

If using this metric with the rrds service, be aware that a value of null (or blank) indicates that no blockettes 1001 were found and the timing quality is unknown. rrds does not accept null values as constraints.

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

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

• Request 24 hours of data for a single N.S.L.C.
• Sum the timing quality values (in percent) from each blockette 1001.
• Return the average of these values:
  

  avg_timing_quality := ( sum[i=1..n] ( timing_qual[i] ) ) / n
  

value – daily average of timing quality values expressed as a percent
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)

When no blockette 1001s are encountered, timing quality reported is NULL for XML/JSON output and blank for CSV/text output. MUSTANG reads individual timing quality values from the miniSEED header; it does not calculate timing quality. When searching by “not equal” value constraints in the measurement service, value_ne=‘numerical number’ does not return null values (e.g., value_ne=0 will not return null values).