I compare the use of Arrival time points Vs the use of "Leading"
point and Arrival position points for the six idealized cases:

The number 1 case refers to the flights illustrated in Case 1b in an earlier
issue of the Oz Report. I score the flights using leading points and arrival
position points and then arrival time points (OzGAP 2005). The left most column
(red) is the first pilot. The second column (green) is the second pilot starting
twenty minutes later and flying as fast. The third column (purple) is the same
first pilot scored with arrival time points (still 1000 points) and the fourth
column (blue) is the second pilot who flies as fast but starts twenty minutes
later and is scored with arrival time points. The second pilot gets a few more
points when arrival time points were used than when leading plus time position
points are used.

Case 2 (both pilots start at the same time but the first pilot is faster than
the second) produces a similar situation in which the second pilot receives more
points when arrival time points are used.

Case 3 (both pilots start off at the same time, but the first pilot is faster
and gets to goal and the second pilot lands before goal) produces a different
result between scoring using leading and arrival position points and arrival
time points. The second pilot gets some leading points when the scoring system
makes them available but doesn't get any arrival time points as he doesn't make
goal. He only gets distance points using the OzGAP 2005 scoring system.

Case 4b (the first pilot starts twenty minutes before the second one but takes
forty minutes longer to fly the course). The fastest (second) pilot gets the
full 1000 points as he gets all the distance, speed, arrival position and
leading points. The first (slower) pilot gets distance, slower speed, all the
leading points and reduced arrival position points. When scored with arrival
time points, the fastest pilot who starts second gets the full one thousand
points. The slower first pilot gets fewer speed points and less arrival time
points.

Case 5b (the first pilot is caught by the faster second pilot at the midway
point and they fly together to goal). The faster (second) pilot doesn't get all
the leading points as he starts behind the first pilot and then stays with him
to goal. He also doesn't get all the departure points as he starts second. When
arrival time points are used, the faster (second) pilot receives all 1000
points, and the first (slower) pilot gets fewer points because of his slower
speed.

Case 6 (the first pilot starts twenty minutes before the second one - one start
time interval - and they both arrive at goal at the same time). The second
(faster) pilot loses some leading points but gets the rest of them. The first
(slower) pilot gets all the leading points, but loses speed points. When scored
with arrival time points, the second (faster) pilot receives 1000 points. The
first (slower) pilot gets fewer speed points but all the arrival time points.

I'll look at whether any of this makes much difference or not in a real
competition.