Version 9 (modified by 13 years ago) (diff)  ,

On task distance
There are basically 2 ways to calculate the distance.
 Task distance calculated as the distance from tp1 to tp3 via the centerpoint of tp2.
 Task distance calculated as the shortest way to fly the task from tp1 to tp3 touching the cylinder edge of tp2 (not going into the centerpoint).
The first is what is normally done now in CompeGPS and RACE.
The second is what is done in FS.
Below is Task 2 from PG Worlds in Manilla 2007:
Tp3 (on top) is with 3km radius. The task distance in CompeGPS as in the official results is: 60.7km. The task distance in FS is 52.5km. The difference is because of CompeGPS calculates total distance as the distance into the center of each turnpoint not taking the cylinders into account. The blue line is the long version with total distance as the excact TP to TP distance. The red line is the shortest distance possible for pilot to fly the task, as done by FS.
We can look at the flights of 3 pilots.
First two did not make the TP3 (pilot1 red, pilot2 black):
The third pilot did just make the TP3 (pilot1 black, pilot3 red):
More close up picture of the turnpoint (pilot1 black, pilot3 red):
According to the distance calculations in CompeGPS (and in the official results) the pilot3 did get 6km longer distance than the other two pilots by just entering into the 3km radius cylinder.
Official results:
Pilot3 : 16,9 km
Pilot2: 11,3km
Pilot1: 10,9 km
FS calculates the task distance as the shortest distance for pilot to fly the task.
The distance a pilot has flown is then the task distance minus the shortest distance the pilot must fly to finish the task.
Results with FS way of calculating distance:
Pilot3: 10.4 km
Pilot2: 9,5 km
Pilot1: 10,0 km
Explained:
Pilot1 lands just outside the circle but closer to course line than Pilot3 and Pilot2.
Pilot1 therefore got a shorter way to go to finish the task than Pilot2 even though she got longer distance to go to the turnpoint cylinder.
Attachments (4)

a1.gif (12.3 KB)  added by 13 years ago.
TaskDistance illustration

a2.gif (5.7 KB)  added by 13 years ago.
TaskDistance illustration

a4.gif (6.0 KB)  added by 13 years ago.
TaskDistance illustration

a3.gif (5.9 KB)  added by 13 years ago.
TaskDistance illustration
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