Data Services Newsletter

Volume 19 : No 2 : Summer 2017

Introducing the IRIS Data Availability Webservice: Quickly find what data is in the archive

Seattle, WA (IRIS) – The IRIS DMC is pleased to announce a new tool for discovering the availability of data in the IRIS archive. The irisws-availability webservice provides detailed timespan information of seismic time series data in the IRIS DMC archive. It provides a missing piece to the archive access puzzle:

Service Returns
fdsnws-dataselect    time series data in SEED format
fdsnws-station metadata for time series data
irisws-availability availability of time series data

Prior to the arrival of irisws-availability users of the IRIS DMC archive would only be able to determine data availability by actually requesting data, by using GOAT (Gap/OverlapAnalysisTool ) or by using the fdsnws-station service. Although GOAT is a useful tool, it is not meant to be run as a webservice. The fdsnws-station service can return data availability extents. However, the extents are based upon when time series data first arrived until it was last received and there may be large data gaps that are not shown (see station service help: availability for more information).

irisws-availability is similar to the fdsnws-station and fdsnws-dataselect services in its calling syntax. It accepts the familiar SEED network, station, location, channel codes and starttime and endtime query parameters as input and returns timespans (start and end times) of contiguous sections of data in microsecond resolution. It accepts both HTTP GET and POST style requests. The web service handles the details of suturing together adjacent timespans based on sample period and miniSEED record start and end times. It is also handles the details of merging overlapping timespans as well as the details of variable sample-rates. It can return data in four formats: text, json, geocsv and sync.

The irisws-availability web service also returns the most recent archive load dates per timespan. This capability is useful for users who wish to maintain synchronization between their local copies of data and what is held in the DMC archive.

Along with providing detailed timespan information, the service also provides an extents level view which returns total date range extents per network, station, location, channel, quality, sample-rate tuple.

Sample Queries

Extents of all network IU, BHZ channel data available in the archive

service.iris.edu/irisws/availability/1/extent?network=IU&channel=BHZ

Timespans of all network IU, BHZ channel data available during the time window 2011-03-11T05:46:23 to 2011-03-11T06:46:23

service.iris.edu/irisws/availability/1/query?network=IU&channel=BHZ&start=2011-03-11T05:46:23&end=2011-03-11T06:46:23&mergequality=true&mergesamplerate=true&showlastupdate=true

Limitations

A primary limitation of the irisws-availability service is that it does not have knowledge of data in the DMC’s realtime data collection system. Consequently, it is not currently useful for reliably discovering data availability for time windows covering approximately the most recent 30 hours. For more information concerning limitations please see the online help

Online Documentation

When getting started with irisws-availability be sure to read the online documentation and help.

by Bruce Weertman (IRIS Data Management Center)