WERA quality control – quality assurance
A significant effort is currently being made by the Ocean Radar Facility to assure quality of HF radar for both the real time data and data going into the archive. Quality control (QC) procedures developed so far for the WERA systems revert radial current maps to the original Doppler Shift and set signal-to-noise constraints based on the consistency with neighbour cells to remove outliers in radial current components. This QC procedure also associates the appropriate Quality Control flags on the data points. Examples of radial maps BEFORE and AFTER the QC, shown below for Tannum Sands WERA site, illustrate the improvement in coverage and consistency using the Ocean Radar Facility algorithm.
Below are four examples that illustrate the differences between the 2 QC routines; Ocean Radar Facility and WERA. All four examples are from the Tannum Sands radar station and radials produced from the Ocean Radar routine are on the left while radials produced from the WERA routine are on the right. The uppermost 2 examples are from 16 June 2009 at 0200 GMT and are shown as example of when the differences between both routines is minimal -- i.e. signal to noise ratio of the sampled domain is relatively high. Whereas the example at the bottom, from 28 May 2009 at 2000 GMT shows a dramatic change between the 2 QC algorithms. The bottom example clearly shows the advantage of using the Ocean Radar QC algorithm over that of the WERA.
Additional QC procedures are being implemented to remove external interferences and further refine data quality for both radial currents, waves and wind maps, which take advantage of the spectral variance reduction from the temporal averaging of the QC Doppler spectra. The feasibility of similar approaches is being investigated for the SeaSonde Direction-Finding systems also. In parallel, QC algorithms are being developed and tested for the surface current maps, based on the temporal and spatial continuity in the data set. Gap-filling techniques are also currently being test.