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Data Acquisition
The NEPTUNE Canada ocean network supports a profusion of instrument types, providing numerous data types and formats. To simplify things, we have boiled all of these down to three general data categories, each requiring a different approach to acquisition and storage:
| Type | Examples | Storage |
|---|---|---|
| Scalar |
Temperature, depth, salinity, current direction, current velocity |
Database table for each data item (measurement), its time stamp and a quality flag |
| Complex |
Multi-dimensional data structures including images, acoustic profiles, current velocity vectors, sonar, etc. |
Files representing snapshots or limited time-lapse |
| Stream |
Linear data streams such as audio (from hydrophones) or video |
Files representing data gathered over a time period |
The DMAS software acquires sensor measurements by connecting to instruments via IP and either "listening" to instrument reports or sending periodic commands.
The Data Acquisition Framework designed to support this high-priority activity is based on an Enterprise Service Bus, using the publish/subscribe model to "chain process" newly acquired data from an instrument. Various elements of the process include:
- interaction with the instrument (driver)
- parsing data strings from instruments into individual data elements (i.e. individual readings)
- calibration
- event detection (optional)
- automated 1st-level data quality control
- archive
The Enterprise Service Bus spans all levels of the observatory, from the shore station to the data centre. NEPTUNE Canada's DMAS data acquisition framework is based on Enterprise Service Bus connections to both varied locations and service functions. (Click to enlarge.)
Event Detection
DMAS is designed for 24/7 connection and interaction with science instruments. Of course, many experiments will depend not only on continuous data, but also the ability to closely monitor various episodes or events when they occur. To facilitate this, DMAS will allow scientists to define automated data assessment rules to do things like:
- check averages
- identify extreme values
- correlate values between sensors
When thresholds, as defined by the monitoring rules, are exceeded, DMAS can then react in a variety of predefined ways, depending on the needs of scientists. Example:
- generate a short notification email
- send a short automated telephone message
- switch on a certain instrument, such as lights and camera
- adjust measurement parameters
This exciting new capability promises to be tremendously useful for scientists and researchers. If you are planning experiments within the NEPTUNE Canada observatory and wish to take advantage of event detection, let us know, and we will work with you to devise an event detection strategy.
