fix bugs in TTL and TTG calculations

aman/sys/aco/Node.py

@@ -176,12 +176,23 @@ class Node:
             if None != star:
                 flightTime, trackmiles, arrivalRoute = self.arrivalEstimation(identifier.Runway, star, weatherModel)
 
-                avgSpeed = trackmiles / (float(flightTime.seconds) / 3600.0)
-                # the closer we get to the IAF the less time delta can be achieved by short cuts, delay vectors or speeds
-                ratio = min(2.0, max(0.0, self.PredictedDistanceToIAF / (trackmiles - self.PredictedDistanceToIAF)))
-                possibleTimeDelta = (trackmiles / (avgSpeed * 0.9)) * 60
-                ttg = timedelta(minutes = (possibleTimeDelta - flightTime.total_seconds() / 60) * ratio)
-                ttl = timedelta(minutes = (possibleTimeDelta - flightTime.total_seconds() / 60))
+                # calculate average speed gain
+                avgSpeed = trackmiles / (flightTime.total_seconds() / 3600.0)
+                avgSpeedIncrease = avgSpeed * 1.10
+                avgSpeedDecrease = avgSpeed * 0.80
+                decreasedSpeedFlighttime = (trackmiles / avgSpeedDecrease) * 3600.0 # given in seconds
+
+                # calculate shortcut gain and add 15 miles for final and base turn
+                currentPosition = Waypoint(latitude = self.PredictedCoordinate[0], longitude = self.PredictedCoordinate[1])
+                shortcutDistance = currentPosition.haversine(identifier.Runway.Start) + 15.0
+                shortcutFlighttime = (shortcutDistance / avgSpeedIncrease) * 3600.0
+                if shortcutFlighttime > flightTime.total_seconds():
+                    shortcutFlighttime = flightTime.total_seconds()
+
+                # the best TTG is the shortest path with the fastest speed
+                ttg = timedelta(seconds = flightTime.total_seconds() - shortcutFlighttime)
+                # the best TTL is the longest path with the slowest speed
+                ttl = timedelta(seconds = decreasedSpeedFlighttime - flightTime.total_seconds())
                 ita = self.Inbound.ReportTime + flightTime
                 earliest = ita - ttg
                 latest = ita + ttl