Monday, 12 January 2009
Evaluation of extinction coefficient algorithms for optimizing reported visibility conditions for air traffic control applications
Hall 5 (Phoenix Convention Center)
This paper examines the potential of utilizing previously measured extinction coefficients over different time intervals for projecting visibility conditions over future time intervals. The focus is on examining visibility conditions during the two-minute future interval considered to be most applicable to aircraft on final approach. This time period is considered representative of the time it takes for a modern aircraft to reach the touchdown point on the runway from the outer marker which ranges from round 4- to 7-nm from the runway threshold. Algorithms for forecasting visibilities for similar time intervals are also desired for use in coasting visibility sensor readings in the event of a visibility sensor outage.
Visibility sensor data, covering many types of natural weather conditions that result in decreased visibilities, are used for the analyses. Properties of visibility data are illustrated via normalized histograms and cumulative distribution plots and the statistical t-test is used to compare average extinction coefficients. The results show that the best predictor depends on the characteristics of the event with a two-minute time interval optimal for many events. Tradeoffs in the frequency of missed alerts and false alerts with differing prediction basis times are also examined.