Redundant multi format data acquisition
What is CAPS?
The Common Acquisition Protocol Server (CAPS) was developed to fulfill the needs to transfer multi-sensor data from the station to the data center. As nowadays more and more stations with co-located sensors like broadband seismometer, accelerometer, CGPS, temperature, video cameras, etc. are build up, a acquisition protocol is required, which can efficiently handle low- and high-sampled data through one unified protocol.
The focus on early warning in the last decade gave the timeliness of data a high priority. This made it necessary to allow backfilling of data (send most recent data first) as well as reducing the size of the data records. These requirements for data acquisition can not be fulfilled by many standard software packages. For example SeedLink, the de facto standard of real-time data transmission widely used to transmit seismic data, can neither handle backfilled data nor supports a variable record size. CAPS fills this gaps as it is format independent, which allows to handle low and high sampled data in parallel and uses index files to keep track of the timely order of packets.
One of the main problem for institutions handling massive data is the downtime during reconfiguration. CAPS reduces the downtime to an absolute minimum and at the same time takes care that no gaps in the data occur. This is realized through two approaches. One is the support of wildcard requests, the other is the buffering of data within the plugins. Wildcard request means, that CAPS can request all data available at the source and doesn't need a specific list of stations. Once the source adds a station, the data is directly transmitted to the target without the need to reconfigure or restart CAPS.
into an archive and provides it to connected clients. The connection between a data provider and CAPS is made through a plugin.
Plugins are independent applications which, similar to clients, use a network socket to communicate with the server. The advantages of this loose coupling are:
For the direct acquisition of data from a sensor the plug-in has to run on the sensor station. This plug-in will send the data either directly to the data center or to local CAPS instance. The advantage of the second approach is:
The ability to connect different CAPS instances simplifies sharing of data. One protocol and one implementation is used for the sensor-to-center and center-to-center communication. In the same way multiple CAPS instances may be operated in one data center on different hardware to create backups, establish redundancy or balance the server load.
The Overview shows (figure web/overview perspective) provides traffic data such as current uploadrate, received bytes and packages. On the right side the same traffic data is displayed as live charts allowing to instantly recognize changes in the data flow.
The Stream perspective shows all data streams including the time window of available data. The list may be filtered to easily find the streams of interest. Also time series data as well as image data may be instantly viewed by clicking on a particular channel entry (figure web/channel view).
CAPS is developed as a standard SeisComP3 application. It uses the SeisComP3 infrastructure for startup and configuration. A GUI application
simplifies the setup and configuration tasks. In addition we offer a full featured web based configuration interface allowing you to control your installation from anywhere using any device running a web browser.
Since CAPS entered the market more and more plugins have been developed. The most import once are: