Big10 is right. The reason Quik’s original equation didn’t work was because it estimated the final 5m based on the average speed of the original 55m rather than estimating it off of an instantaneous speed closer to the end of the 55m. When you take a split later in the race (say the last 5-10m) and estimate 5-10m after that point, you can get a pretty reasonable estimate for 2 reasons:
1. You are making an estimate based on an instantaneous speed (5m or maybe even 10m) rather than average speed.
2. You are extrapolating the estimation to a very limited distance (5-10m beyond the original distance). The further you attempt to extrapolate the split estimation, the less accurate it is likely to be. This is why it’s extremely difficult to make estimations for the 100m based off of 55m times.
As for the 0.46-0.49 add-on times, they are actually decently accurate. This is because they are based on the 2 points I mentioned above. That is, the given governing body lays out a qualifying time for the standard distance (in this case the 60m). They know that to run the qualifying time for the standard distance, an athlete will almost certainly have to attain a given instantaneous speed. Knowing this, they can make a reasonable estimatation for a short distance. The logical reason that different governing bodies or associations would have different conversion factors is because they are likely basing the split time off of different qualifying times for the standard distance. In the examples given, I’d be willing to bet that the 60m qualifying time associated with the 0.49 second conversion is slower than the 60m qualifying time associated with the 0.46 second qualifying time.
While this system isn’t perfect, the conversion from 55m to 60m isn’t likely to be too far off for a given speed range (in this case, those people who could potentially qualify). Making an estimation for 100m based on 55m would be another story though.