Swimmers train very hard and it is important that their results are correctly recognised.
Different timing methods can record slightly different times. This article explains why and which is more accurate.
Stopwatch timing often records times faster than actual
Fully manual stopwatch timing is one of the least accurate methods for recording a swim race. On occasions differences of over 1s from actual have been observed.
A timekeeper with a manual stopwatch must accurately press a button twice – once at the start of the race, and again at the end. It is easier to be accurate at the end of the race than at the start.
Often timekeepers are more late at the start of the race than at the finish, which means swimmers are often recorded with slightly faster times than they actually swam.
Due to the speed of sound, at the end of a 50m pool there is a delay of 0.15s before the starting signal sound is heard by timekeepers. Timekeepers are therefore instructed to start their watches upon the starting light, not sound.
It is very difficult for even the most diligent timekeepers to remain alert and accurate throughout a long meet.
Additional timekeepers are often rostered on each lane to improve accuracy by reducing variability. Although this is theoretically better, the fundamental challenges with fully manual timing remain.
Semi-automatic (button) timing eliminates any start errors
Semi-automatic timing (‘SAT’) is commonly used by the popular Colorado Dolphin system, and the push button systems used at major aquatic centres.
Semi-automatic timing eliminates any starting time errors by triggering automatically at the starting signal. Timekeepers only need to press once, at the end of the race.
Semi-automatic timing records times slightly slower (0.06s) than actual on average, due to the human reaction time between observing the finish and pressing the button. 95% of times are recorded -0.12s/+0.24s of actual.
A study of semi-automatic timing showed that accuracy varies by lane, stroke and time of day.
Rostering 2 timekeepers per lane gives slightly improved performance. Early indications are that 3 is not as good as 2. This counter-intuitive result requires further study.
Touchpads are considered the gold standard
Touchpads timing (Automatic Officiating Equipment ‘AOE’) starts automatically at the starting signal and stops automatically when the swimmer touches the wall at the end of the race. For elite swimmers at major events using well maintained equipment they generally operate very well.
For smaller and less experienced swimmers, and where not regularly maintained, pads can be less reliable. Touchpads are actually pressure pads constructed by plastic pressing metal strips together to close an electric circuit, and spend much of their life in chlorinated environments.
A study has shown that touchpads fail for 1 in 20 swims on average, but this can vary enormously between lanes and strokes. For this reason, backup timekeepers using semi-automatic timing are rostered alongside touchpad systems.
Backup times are used when either the touchpad has not produced a time, or is known to have failed, for example is believed to have missed an earlier ‘soft’ touch by the swimmer. Standard operating practice is to investigate times only where there is at least 0.30s difference between pad and backup time.
Olly Timing
Olly Timing uses high speed video. Timing starts automatically at the starting signal, and stops at the photographic frame when the swimmer touches the wall at the finish.
This is very similar to the high speed video (‘HSV’) timing systems used at major national and international events for backup timing. There are two main differences.
Olly Timing currently has a precision of 0.02s which is slightly larger than the 0.01s for HSV. Olly uses artificial intelligence (‘AI’) to rapidly identify the approximate finish time, usually 0.30s accurate, before the Olly Timing operator manually reviews and sets the official time.
A study of over 6,000 swims has shown that Olly Timing records 95% of times within +/- 0.18s of the actual time. This is slightly better than 1 timekeeper using a semi-automatic system, and much better than 1 timekeeper using a fully manual (stopwatch) system.
Olly Timing operators are humans and can make errors. All swims are captured on video and can be reviewed if required.
Olly Timing does occasionally record incorrect times. These are usually very incorrect, often by several seconds, or record times against empty lanes. This mostly occurs when a swimmer was not spotted finishing and the time of the last frame of the video was recorded.
Swimming NSW have confirmed that Olly Timing may be used for all official times except State records.
So what?
- Timekeeper times should usually be treated as ‘unofficial’ and probably different from the official times.
- Remember that precision and accuracy are different. Just because a time is quoted to 0.01s does not mean that is its accuracy.
- Swimmers attempting to set a State record should have 3 timekeepers on their lane.
- Errors do occur. Unlike in the past, Olly Timing video now allows for results to be reviewed. In general times are not re-evaluated unless there is a 0.30s difference from semi-automatic timed results.
- Good officials always want to achieve the right result for the athlete. Do not worry about raising queries, but also respect their time. It’s always best to check and query results during the meet.
