This metric reports the number of unique sample values over a 24-hour window. A very low number of unique count values may indicate a dead channel that is not recording ground motion.
A seismic channel that records a time series with only a single (or very few) unique values is unlikely to be recording ground motion. As such, it can be an indication of instrument malfunction. This is not applicable to state of health channels such as VM mass positions, although the metric returns values for these also.
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 or IRIS PH5 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.
- Identify and report the number of unique amplitude values for the requested data:
For i=1,N samples in the time series x: length(unique(x(i),...,x(N)))
value – number of unique sample values
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)