https://www.olympic.org/news/double-gold-medal-joy-as-oleksi...
So to solve this they just don't measure beyond hundreds (no human can swim fast enough that the distance they travel within 0.01s could make a difference). And thus can not use photo finish either as again the lanes are not guaranteed to be the same length.
https://interestingengineering.com/significant-digits-and-po...
edit: In other sports like running it is easy to have accurate track length as you just paint the lines after building the track so you can have it as accurate as you want (+photo finish). In swimming it just does not work like that.
https://www.telegraph.co.uk/content/dam/news/2016/08/13/drys...
(Drysdale is in the black boat).
(Of course, this would totally ruin the sport for spectators.
Following this logic, for any sport with no interaction, everyone could just stay home and run around their own track whenever they feel like and just send in their times to a central record keeper.)
That has always bothered me that there are some calculations/arbitrary numbers based on the wind... to a point the length of the ramp gets adjusted. I recall when the V shape was introduced, initially it was shunned by the judges for bad style (negative points), regardless it was obviously aerodynamically better. However, swimming would also be affected as the water temperature won't be constant either.
(But you are right about outdoor pools. They are much more of a hassle to adjust the temperature for.)
Let’s say real times were 58.994999 and 58.995000 seconds. The first gets registered as 58.99, the second as 59.00. Actual difference is a millionth of a second, or, at 2 meters a second, 2μm.
I think they do this in swimming more because swimmers, certainly at shorter distances, more race themselves than their competitors. That’s a huge difference with road cycling, where typically the front riders in a sprint could get over the finish earlier, if they wanted to, but don’t want to do that, as, if they did that, their competition would tail them up to the last few meters and then jump over them.
Rowing is somewhat of a middle ground. They do use finish photos, even though there’s the same. “Tracks aren’t guaranteed to be the same length” problem as in swimming.
A famous example is the men’s scull final in the 2016 Olympics: https://www.olympicchannel.com/en/video/detail/mahe-drysdale...
I don’t understand why you think it’s easy to have accurate track length in running. Temperature may affect track length. A lot more importantly, I don’t think it’s even doable in events where runners all start in their own track but are allowed to move to the inner track after x meters. But again, it’s less important there because runners race against each other there more than in short swim races.
How do you achieve a million frames per second? Even analog input (like touching - which would be capacitive [hence more tolerances]) will have a very hard time registering that, just based on cable and PCB traces length, temperature differences (which affect silicon and resistance in general). 7 digit precision is a non-trivial task for non-controlled environment. For example 8.5 digit voltmeters take one 1 minute for a single measurement and they have to have extremely good temperature controls.
Then for the microsecond precision you have to consider the speed of sound just to propagate to participants to hear the gun.
Side note: my HP 3458A can do a small handful of 8.5 digit DCV measurements per second.
I thought they had like 100k samples a second. Is it really sufficient for 8.5 precision?
Edit: perhaps measurement should be confined only to relative finish between the participants, e.g. finish within 1ms should be considered the same (regardless if they fall in the same hundreds of a second bucket)
On thing I know with perfect precision: HP/Keysight knows more than me about this. :)
In swimming, the start and finish are both fixed physical objects that the swimmer must touch (though in all events except backstroke, the start is a bit weird because it's outside the pool).
In rowing, the finish line is an imaginary line much like cycling or running. While at the Olympics there are 'clogs' to hold the bows of the boats which drop down at the start:
https://www.polaritas.com/products-and-services/automatic-st...
a race official is always required to certify that the bows are aligned, which is why the gates are transparent (and the system includes video cameras to help this official).
In rowing you row between 2 imaginary lines. You don't even have to get the distance of these lines perfectly just make sure they are both in the same direction and neither boat gets the advantage.
With swimming you have to build a 50m long and quite wide concrete structure that has straight angles at all 4 corners and has perfectly straight walls. This is actually much harder to do then it sounds.
Nitpick: that is not correct. If the shape of the course is a parallellogram, the shortest course between the short sides is perpendicular to those sides. Teams in some of the lanes my be able to pick such a course. For example:
________________________________
/A B/
/ /
/ /
/C D/
——————————————————————————————
It is very unlikely they won’t hinder other crews if they cross all lanes, but they might just cross lanes of a few much slower boats.
That’s all theoretical, though. The net gain on a normal course would be very, very small, and buoys will typically hinder crews that would try this so much that it wouldn’t be worth it, to start with.
Also, for the true nitpicker, “the right direction” can be difficult. Drawing equidistant lines on a globe isn’t trivial (I don’t think the effect will be large for a 2km course on earth, though)
It would be crazy expensive to make the pools to such a small tolerance, perhaps, but it is not the length of the pool that actually counts, is it? It is the distance to the touch pad that counts.
Would it be crazy expensive to make the touch pad mounting system adjustable so that the position of each lane's pad could be adjusted to millimeter or even sub-millimeter tolerances?
But yes in general new competition pools are built to be slightly larger than 50m and you just adjust the pads at the ends.
On one side it's unfortunate that technological details and possibly human error make it hard or controversial to decide the winner for this race, on the other side this event has kept the cycling community talking for 3 weeks (even HN is talking about it right now). And most likely in the next few months or years we'll see some rule/regulation changes to handle these cases better. Just like in politics, something needs to happen first before action is taken. All the recent rule changes were triggered by dangerous crashes or other events.
And imho all of this combined makes pro-cycling one of the most exciting forms of entertainment to watch or follow.
A little side note: Many amateur races don't have photo finish equipment. In my race days sometimes not even a camera, and 3 race officials would stand on a little platform above the finish line with voice recorders just calling out jersey numbers and then get together in a room for 20 minutes to compare recordings and compile the final result. Draws were much more common back then.
edit: all of the previous races and media coverage and drama and the first 250k in this race have led to this super exciting final 1k that is ultimately decided by millimeters. To me that is beautiful.
In this case it wasn't immediately clear who won and the officials had to make a call under pressure with millions of people waiting. They called Van Aert as the winner based on the imperfect data they had. Was it the right call? Maybe, maybe not. In an alternate timeline they might have called Pidcock, or a draw, or a redo of the last 1km.
The takeaway is that this rare occurrence happened and sparked lots of discussion, which hopefully leads to technological and/or regulation changes to could handle these occurrences better in the future. I would call that progress.
Interestingly, technology makes this trivial these days:
Pop a cheap Android phone on a tripod, and with the right software (or even just taking a video), you have a decent approximation of photo finish equipment.
(I say 'trivial', because a smartphones with the required capabilities are basically free, if you take an old, used one.)
Eg measure how fast bubbles rise in honey at various temperatures to calculate its viscosity. Or: drop various big blobs of water from a height and analyze what happens. Or, figure out at what windspeed candles blow out.
Relatively simple things, but not usually covered in high school physics classes.
Anyway, it was amazing how many experiments became so much more feasible than even a few years prior, because cheap digital cameras were available.
Oh, this also reminds of how ufo and Loch Ness and Yeti sightings have become so much rarer these days, because people demand proof.
Still, I think there will always be a place for a stone-faced commissaire with a clipboard, freezing their ass off in the finish-line rain, watching the bunch draw near.
I always assumed the transponders were mostly used for GC timekeeping in multi-day stage races and maybe help automate the initial results shown on TV post-finish.
The live telemetry (wattage, speed, heartrate) we've seen in some races the last few years are also very interesting. But that's probably a different tech stack from transponders used for timekeeping.
Some manufacturers claim millisecond accuracy, which is plenty for (say) counting laps in cyclo-cross, or for timing many BMX events; but they're not enough to distinguish the places in a >70km/h field sprint for the finish line.
Some mass participation events like public marathons may use low-cost/disposable passive transponders e.g. ones embedded in the bib number; these are more like a typical RFID chip, having a longer (and rather jittery) wake-up time, in part because they draw power from the mat itself, and a much lower transmission energy. They're more easily disrupted by environmental conditions, or when passing in large groups, or even by sweat & skin contact.
Telemetry from onboard bike computers and sensors is indeed a completely separate stack, and can be anything from a bluetooth relay by phone app over cellular, to a dedicated vendor-specific box with its own SIM card and a short-range radio to signal the team car. The onboard sensors are generally using ANT or BTLE to talk to the head unit aka "bike computer" that aggregates, records, displays, and relays the data. Speed may be calculated by GPS/GLONASS/etc, or sensed by wheel rotations e.g. using a spoke magnet or even hub-based rate ticker, in which case the necessary measure of precise wheel diameter may still be calibrated by the head unit using GPS. Power is not measured directly but inferred e.g. by integrating a dynamometer within the crankarm to compute power from strain & cadence. Some units also capture barometric pressure to estimate altitude, and this may be considered more accurate than GPS right up until you ride through a pressure front and it goes bananas. Some bicycles e.g. those with electronic/wireless shifting may also report their current chainring & sprocket selection, and finally you can overlay all this excruciating near-real-time detail onto the Gopro video feed from your handlebars/seatpost cameras and livestream it over cellular networks and thence to the world-wide peanut gallery.
To sum up, there's an awful lot of 2.4GHz activity going on in the pro peloton, and I hereby deny ever having paired a second bike computer with the HR strap and power meter of my nemesis in order to know when the bastard was too tired to follow my attack, no sir