Summary
This metric reports the percentage of data available for each 24-hour window calculated at query time. 100% data available means that data for the reported start and end time is complete. It calculates 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 web service or the service.iris.edu/ph5ws/availability web service.
In contrast, the standard MUSTANG percent_availability metric retrieves and analyzes the archived time series in order to calculate availability, which is a much slower process. Measurements for percent_availability are calculated according to a schedule and updated regularly, but their values reflect the completeness of the archive when the measurement was made (lddate) rather than at query time.
The ts_percent_availability metric is currently a prototype that will eventually replace the standard MUSTANG percent_availability metric.
Uses
ts_percent_availability values can be averaged to give data completeness for a channel over an integer number of days. The metric also indicates whether or not data for a given channel/day is available for request from the IRIS DMC.
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 archive database time series index (ts_index)
SEED Channel Types – All Time Series Channels
Algorithm
- Assemble availability web service trace extents for 24 hours on each matching N.S.L.C.
- Sum the data gaps in seconds for this period of time.
- Calculate the percentage from the ratio of data found (omitting gaps) to data expected for the full day:
percent_available = 100 - ( 100 * gap_seconds / total_seconds )
Metric Values Returned
value – availability of data expressed as a percentage
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
Notes
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.
