NSF National Geophysical Facility MUSTANG metrics Web Service Documentation

This metric counts the times this clock flag is set from 0 (default) to 1 in the fixed section of the miniSEED header. A flag value of 1 indicates that the GPS has locked with enough satellites to obtain a time/position fix. Not all dataloggers set this flag.

PH5-format data does not include miniSEED flag information; this metric will always return a value of 0 for data in the EarthScope PH5 archive.

This metric can be used to identify dataloggers with faulty GPS clocks and data days with questionable timing. Lack of a GPS lock does not necessarily mean that a datalogger’s internal clock is known to have drifted significantly from GPS time. Some modern VCXO clocks may not drift significantly for days after their last GPS lock.

A value of 0 (zero) can either mean that:

• the datalogger detected 0 instances of this condition, or
• the datalogger does not set this flag, so it is unknown whether or not this condition occurred.

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

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

• Request 24 hours of data for a single N.S.L.C.
• Count and report the number times this binary flag is set to 1.

value – number of times this flag is set to 1 that day
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)

Not all dataloggers set this flag. For those that do not, a value of 0 does not necessarily mean that the GPS clock is unlocked.