getAvailability: Retrieve Channel metadata from IRIS DMC

In IRISSeismic: Classes and Methods for Seismic Data Analysis

Retrieve Channel metadata from IRIS DMC

Description

The getAvailability method obtains channel metadata for available channels from the IRIS DMC station web service and returns it in a dataframe.

Usage

getAvailability(obj, network, station, location, channel,
                starttime, endtime, includerestricted,
                latitude, longitude, minradius, maxradius)

Arguments

obj	IrisClient object
network	character string with the two letter seismic network code
station	character string with the station code
location	character string with the location code
channel	character string with the three letter channel code
starttime	POSIXct class specifying the starttime (GMT)
endtime	POSIXct class specifying the endtime (GMT)
includerestricted	optional logical identifying whether to report on restricted data (default=FALSE)
latitude	optional latitude used when specifying a location and radius
longitude	optional longitude used when specifying a location and radius
minradius	optional minimum radius used when specifying a location and radius
maxradius	optional maximum radius used when specifying a location and radius

Details

The getAvailability method uses the station web service to obtain data for all available channels that meet the criteria defined by the arguments and returns that data in a dataframe. Each row of the dataframe represents a unique channel-epoch. This method is equivalent to the getChannel method with the following additional parameters attached to the url:

&includeavailability=true&matchtimeseries=true

Each of the arguments network, station, location or channel may contain a valid code or a wildcard expression, e.g. "BH?" or "*". Empty strings are converted to "*". Otherwise the ascii string that is used for these values is simply inserted into the web service request URL. (For non-available channels use getUnavailability.)

For more details see the web service documentation.

Value

A dataframe with the following columns:

network, station, location, channel, latitude, longitude, elevation,
  depth, azimuth, dip, instrument, scale, scalefreq, scaleunits, 
  samplerate, starttime, endtime, snclId

Rows are ordered by snclId.

The snclId column, eg. "US.OCWA..BHE", is generated as a convenience. It is not part of the normal return from the station web service.

Note: The snclId is not a unique identifier. If the time span of interest crosses an epoch boundary where instrumentation was changed then multiple records (rows) will share the same snclId.

Author(s)

Jonathan Callahan [e-mail]

References

The IRIS DMC station web service:

https://service.iris.edu/fdsnws/station/1/

This implementation was inspired by the functionality in the obspy get_stations() method.

https://docs.obspy.org/packages/autogen/obspy.clients.fdsn.client.Client.get_stations.html

See Also

IrisClient-class, getChannel, getUnavailability

Examples

# Open a connection to IRIS DMC webservices
iris <- new("IrisClient")

# Date of Nisqually quake
starttime <- as.POSIXct("2001-02-28",tz="GMT")
endtime <- starttime + 2*24*3600

# Use  getEvent web service to retrieve events in this time period
result <- try(events <- getEvent(iris,starttime,endtime,6.0))
if (inherits(result,"try-error")) {
  message(geterrmessage())
} else {
  events

# biggest event is Nisqually
  eIndex <- which(events$magnitude == max(events$magnitude))
  e <- events[eIndex[1],]

# Find all BHZ channels collecting data at the time of the quake and within 
# 5 degrees of the quake epicenter
  result <- try(channels <- getAvailability(iris,"*","*","*","BHZ",starttime,endtime,
                            lat=e$latitude,long=e$longitude,maxradius=5))
  if (inherits(result,"try-error")) {
    message(geterrmessage())
  } else {
    channels
  }
}

IRISSeismic documentation built on Oct. 16, 2022, 1:09 a.m.