Download About IDA Communications Stations of the IRIS/IDA Global

About IDA Communications
Stations of the IRIS/IDA Global Seismographic Network are configured as
nodes on the Internet to facilitate access to the Internet and its associated
long-haul telecommunications infrastructure. By developing data
acquisition and transmission around the Internet’s TCP/IP protocol suite, the
task of data collection from remote locations reduces to one of bringing the
Internet to the station, a problem for which a multitude of off-the-shelf
solutions exist.
Nodes at IDA stations are connected to the Internet over a variety of circuits,
including through:
● a local area network (LAN) already on the Internet
● a dedicated (leased) telecommunications circuit to an Internet
“point-of-presence”
● a dial-up telecommunications circuit to an Internet “point-ofpresence”
● a satellite circuit for those stations unreachable by existing
telecommunications circuits
Data acquired via telemetry may be used for such diverse purposes as:
tsunami warning:
When large earthquakes occur at sea, they may generate very large
seismic sea waves that pose great danger to many persons around the
world who live in coastal communities. Prompt transmission of the
seismic data permits experts to locate earthquakes quickly, assess the
likelihood they have generated a tsunami, and predict when the
destructive wave will arrive. Such predictions have already saved
numerous lives.
emergency response:
Prompt and accurate location of earthquakes allows emergency
personnel to better plan their response to disasters that occur in remote
regions of the world.
monitoring underground explosions:
Seismic methods are used to monitor adherence to nuclear test ban
treaties. When a nuclear device explodes underground, the resulting
shock wave can be detected by seismic instruments over great
distances.
About the IDA NRTS
The IDA Near-Real Time System (NRTS) is a body of software developed
at UCSD with funding from IRIS to provide GSN stations with Internet
access and data request management capabilities. The software is in a
mature state having been used by IDA for over seven years. During this
period, it has undergone one major redesign and evolved into a robust set of
code.
NRTS runs on any POSIX compliant UNIX platform. It accepts a data
stream as input, writes the data to a disk loop, and then services data
requests from that loop. The user may choose from a variety of input
formats or, using a library of functions provided with the package, adapt the
input data request server to accept data in whatever the native format is,
provided that stream consists of packets with fixed-length header and data
segments. Once in the loop, data may be requested, either in segments or
continuous feeds, in miniSEED, SAC, CSS, or GSE (Alpha or Beta)
formats. If a continuous feed is requested, those data are passed on with
little additional latency. Each packet input to the NRTS host is immediately
output by the data request server.
A computer running NRTS may be configured either as a station host or as a
hub. A station host accepts data locally and stores that data within a disk
loop of configurable length and limited only by disk size. The host's data
server can satisfy requests for any data retained within that disk loop. On
many IDA stations, the loop length is set to one week. A hub accepts data
feeds from one or more station hosts. The hub's data server may accept all
or part of the data available from a given station host. The amount of data
transferred to the hub is only limited by the bandwidth and cost of the circuit
connecting host and hub. There are currently four principle NRTS hubs: one
run by IDA in La Jolla, one by EME in Obninsk, one by the Harvard CMT
group in Cambridge, and one by IRIS HQ in Washington.
About the AutoDRM
The IDA Near-Real Time System (NRTS) has the capability to service data
requests made via automatic data request manager (AutoDRM) software.
Data requests may be directed via email to either a hub or a station host as
described above. If a hub's data server cannot satisfy a request from data
already transmitted to that hub, then the data server consults an ordered list
of NRTS data servers known to handle data from the desired station(s).
These servers may be running either on the station host or on other NRTS
hubs. In cases where the circuit to a station is bandwidth limited, it is
desirable to direct data requests first to the hub rather than the station. All
requests that can be satisfied at the hub are fulfilled from there, and only
those data not at the hub already are requested from the station, thus
avoiding duplicate transmission.
For further details and to receive a manual of information about the
AutoDRM configuration at IDA, send email to:
[email protected]
and include the word “help” in the body of the message. A manual will be
sent to you by return email.