Table 15 shows a similar summary table for twilight conditions. As with daytime cases, the baseline classifier has the highest clear-sky PPC (96.7%) but also the highest cloud and ice MC values (5.5% and 14.2% respectively). Introducing a third class along with the daytime textural modification significantly reduces the cloud and ice MC values to close to zero but also reduces the clear-sky PPC to 59.7%. In this UC 112 case the current ARC cloud screening outperforms the daytime textural modification with a clear-sky PPC of 78.7% (compared with 62.1%) and a adenosine diphosphate (ADP) cloud and ice MC of 0.0%.
A summary of the twilight image classification statistics for algorithms applicable to all ATSR instruments including a comparison with the ARC cloud screening.AlgorithmClear-Sky PPCCloud MCIce MCOverall accuracyBaseline Classifier96.68%5.51%14.17%91.53%Three Way Classifier59.74%4.5%0.0%86.91%Daytime Textural Modification62.1%0.22%0.0%91.62%ARC Cloud Screening78.69%0.0%0.0%93.89%Full-size tableTable optionsView in workspaceDownload as CSV