The conductivity cell on the Seabird CTD 16+ 4996 located on the Digital camera platform (DCF2-01) in Saanich inlet was plugged between April 28th ~1500 and May 3 ~1400 UTC. The conductivity sensor data (along with derived data i.e Salinity, density, sigma-T and sound velocity) are flagged as bad.
On June 23, VENUS released the option for users to select quality controlled scalar data plots from the Download Data page. Selecting the Quality Control parameter “Clean” returns a plot with all values that are deemed good, removing flagged values. Selecting “Raw” for the Quality Control parameter returns a plot with all values regardless of flag value, but “Bad” values are visualized with a red flag indicating the poor data quality. This option is only available for plots as Quality Control flags are returned with all other data products. Below are examples of the returned plots for “Clean” vs “Raw” for salinity data from the Saanich Inlet VIP in 2010:
 Clean |
 Raw |
One of the problems facing a real-time oceanographic observatory is the ability to provide a fast and accurate assessment of the data quality. The VENUS Coastal Network is in the process of implementing measures of real-time quality control on incoming scalar data that meet the guidelines of the Quality Assurance of Real Time Oceanographic Data (QARTOD) group. QARTOD is a US organization tasked with identifying issues involved with incoming real-time data from the U.S Integrated Ocean Observing System (IOOS). A large portion of their agenda is to create guidelines for how the quality of real-time data is to be determined and reported to the scientific community. VENUS is striving to adhere to the QARTOD’s ‘Seven Laws of Data Management’ to provide trusted data to the scientific community.
QARTOD’s Seven Laws of Data Management:
- Every real-time observation distributed to the ocean community must be accompanied by a quality descriptor.
- All observations should be subject to some level of automated real-time quality test.
- Quality flags and quality test descriptions must be sufficiently described in the accompanying metadata.
- Observers should independently verify or calibrate a sensor before deployment.
- Observers should describe their method / calibration in the real-time metadata.
- Observers should quantify the level of calibration accuracy and the associated expected error bounds.
- Manual checks on the automated procedures, the real-time data collected and the status of the observing system must be provided by the observer on a timescale appropriate to ensure the integrity of the observing system.
Real-time data quality testing at the VENUS Coastal Network includes tests designed to catch instrument failures and major spikes or data dropouts before the data is made available to the user. Real-time quality tests include meeting instrument manufacturer’s standards and overall observatory/site ranges determined from previous year’s data. Due to the positioning of some VENUS instrument platforms in highly productive areas, we have also designed dual-sensor tests to catch conductivity cell plugs which cause a sudden drop in conductivity.
The quality control testing at VENUS is split into 3 separate categories. The first category is in real-time and tests the data before the data are parsed into the DMAS database. The second category is delayed-mode testing where archived data are subject to testing after a certain period of time. The third category is manual quality control by a VENUS data expert.
Continue reading QAQC for VENUS Scalar Data
