Sonar data systems specialists process sonar data in the shipboard computer lab.
The Scientific Computer System (SCS) is a high-powered computer system that collects, processes, displays, and archives data from the navigational and scientific sensors on NOAA ships. NOAA developed this system to modernize and standardize data collection on its primary ocean and coastal research vessels.
The number and type of sensors vary according to each ship and its particular mission, but they commonly include oceanographic, atmospheric, navigational, and fisheries data instruments. The ability of the SCS to integrate and display both raw and processed information is vital to safe navigation and scientific applications both during and after the mission. Just as importantly, selected data are sent electronically to NOAA data centers where they are integrated in weather and sea-state forecasts and distributed to the public.
Two computers provide the backbone to the SCS. One collects and processes the incoming sensor data while the second archives it, making the data available to scientists for real-time manipulation and processing. The software the SCS uses has been customized to work with the wide range of instruments aboard each NOAA vessel. Both raw data and processed information can be viewed in either text or graphical forms at numerous computer stations networked throughout the ship. Both SCS computer systems are identical in their configuration so that in the event of a failure to the primary system, the backup can resume data collection immediately.
Two primary types of data logging are supported by SCS – "continuous" data and "event" data. Data that are vital to safe navigation are permanently integrated into the system, recorded and processed on a continuous (i.e., real-time) basis. Examples include information from the global positioning system (GPS), gyrocompass, water depth indicators, and meteorological sensors. In contrast, event data are recorded from instruments used on an "as needed" basis; for example, a water quality sampling device, such as a "CTD" that measures conductivity and temperature at different depths, or a plankton sampling net towed behind the ship. At each step of the event (including start, stop and interim marks), snapshots of key sensor data are automatically recorded. Thus, the user has a complete digital record of the event.
The SCS can also calculate parameters based on raw data collected from the various ship’s sensors. This type of data is referred to as "derived." The relationship between raw data and derived data can be illustrated in the determination of true wind speed and direction while the ship is under way. As the ship is sailing, an instrument called an anemometer collects raw data combining the apparent wind speed and direction caused by the forward motion of the ship (e.g., south at 10 knots), plus the actual magnitude and direction of the true wind (e.g., easterly at 15 knots). The SCS, integrating the ship’s other navigational sensors, can extract out the wind speed and direction due to the ship’s motion. The derived data, then, depicts the wind’s "true" speed and direction. The SCS can also automatically create statistical summaries (e.g., averages) of instrument measurements.
Three types of sensors are commonly linked to the SCS. These include navigational, meteorological, and oceanographic instruments.
Global Positioning System (GPS). The GPS indicates the ship’s position in space. The GPS is a satellite-based system capable of determining location.
Gyrocompass. A component of the ship’s navigational system, the gyrocompass, helps to maintain heading (i.e., direction) on the intended course.
Fathometer. The ship usually has more than one instrument for determining water depth, given its importance to safe navigation.
Velocity Profiler. This instrument records the vessel’s speed. The ship’s "speed over ground" indicates its forward motion plus or minus water current speeds. The open water speed of most larger NOAA ships is approximately 10-14 knots.
Barometer. Typically mounted above the ship’s bridge, the barometer senses atmospheric pressure, an indicator of changing weather conditions.
Anemometer. Mounted above the ship’s bridge, the anemometer records wind speed and direction.
Water Temperature. Sensors mounted to the ship’s hull measure temperature just below the water surface.
Salinity. Salinity describes the concentration of salt in the water column. Salinity values are near zero in freshwater environments and usually range from 33-36 parts per thousand in ocean waters. Salinity is a derived data product. Sensors mounted to the ship’s hull measure conductivity (a measure of the water’s ability to transport an electrical current). When combined with water temperature and water density, conductivity can be used to calculate salinity.