Some scientific analysis of Mao's 3A
- Thread starter Bennett
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Actually for simple minded things I only quote numbers and ranges of numbers to 1/10 sec (or maybe half of that).
For ball park numbers I start with a stop watch and average many jumps. That defines the scope of the measurement problem.
Then, for precise measurements I use high resolution, high speed machine vision cameras with frame rates up to 300 frames per second. With a calibrated frame rate and knowing the takeoff frame and landing frame I get the time in the air to about 5 msec. Using the whole clip I can also measure rotation rates and accelerations in jumps and spins. Am working on combining multiple cameras to determine jump trajectories and other parameters in a program, the plan being to set up a measurement program in a local rink similar to what is done at the OTC in Colorado Springs.
How the images get turned into usefull numbers is something I keep close to the vest, except I will share it involved doing a frame by frame analysis where each frame in the clip is extracted and converted to an image array on which various machine vision and image exploitation methods are applied. We write our own software for this purpose.
In the simplest terms it is similar to what I described one could do with a YouTube video, except for my cameras, I have higher resolution images and higher frame rates, and a calibrated system where I know the camera characteristics, the locations of the cameras, the rink geometry, etc. so everything is fully calibrated. (And believe me, getting a useful answer is a lot harder than saying I know how high someone jumps because I know the length of my leg and I look at them really, really carefully!)
I am not going to say another researcher is wrong without measurements of my own to justify my position, or more details about what he did -- particularly when they are in a lanquage I do not understand and filtered by a reporter who probably doesn't understand anything he was writing about.
However, I think I have been clear that IMO the numbers in the article don't make much sense -- and it should be obvious my intention to make a measurement myself is not motivated by a belief the article and its implications are correct.
If the translations are correct, there is a whole lot of stuff in the article that is not strictly correct in addition to the numbers, but that is probable the reporters fault. The abstract a few posts up is much more reasonable and consistent with current knowledge of the mechanics of jumps -- but also the content is not particulary new information.
But I ain't gonna say what Mao may or may not have done on the day she got measured for the study, or in the competition that may have been studied. For all we know these numbers are based on a couple of jumps on a bad day that have nothing to do with how she jumps most of the time. (Send me a private message during Vancouver to remind me and I will tell you what I measure there.)
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:no:
Your sarcasm is so out of place.
If someone jumps directly in front of you and the bottom of their outstretched feet reach the top of your head, would you not agree that the height of that jump is equal to how tall you are? (There actually is no way to disagree with this, since it is fact, but you seem to have doubts)
Likewise, if you know the length of your body parts (*ahem*) such as the distance from the bottom of your foot to your knee, it's quite easy to tell that someone is jumping much more than 10 inches off the ice if they jump directly in front of you and their blades are higher than your knees.
I can't tell you exactly how high Mao jumps and I don't need to. An estimation is enough - I was simply responding to why the Original Post of this thread is incorrect.
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- Jun 21, 2003
That is another interesting question. Can a skater spin faster in the air, after a powerful launch, than on the ice? It seems like she should be able to.
With the proper camera combinations and angles in a controlled setting, yes --but nothing that is practical at this point for competition.
That is a really good question! Speculation only ...
The maximum rotation rate occurs when the skater minimizes their moment of inertia, and in a jump and upright spin, the minimum moment of inertia is about the same.
But the initial angular momentum that drive the jump and the spin is likely to be different. So the first question is can the skater develop more initial angular momentum entering a spin or taking off on a jump? My guess is they could develop more angular momentum entering the spin.
But in the spin, you have the friction on the ice that impedes the rotation, that does not exist in the air, so that would favor the jump. In a jump, the maximum rotation rate is achieved very quickly (in a fraction of a second), while in a spin skaters often take several rotations to get centered before they fully pull in to increase the rotation rate. All these rotation cost angular momentum in the spin.
So my wild guess is in principle a spin could develop a greater rotation rate, but unless the skaters centers quickly and has a really good edge in the spin, they will not reach the maximum potential rotation rate.
What a fun thing to try and measure!
And speaking of rotation rates, I vaguely recall being told at one point that Lucinda Ruh had been measured a few years ago at 8+ rotations per second in a fast upright spin. But my memory may be faulty on that.
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http://www.youtube.com/watch?v=F9hKjSou73Y
They picked the fastest segment, and it looks a lot faster than Mao Asada's revolution on air.
Also, there's the equipment to measure revolution. Maybe Mao should be studied if she can spin 7.7 rev per sec.
And just because, Yasuo Ikegami.
They picked the fastest segment, and it looks a lot faster than Mao Asada's revolution on air.
Also, there's the equipment to measure revolution. Maybe Mao should be studied if she can spin 7.7 rev per sec.
And just because, Yasuo Ikegami.
good luck finding a TV with true 240Hz. let alone 300Hz frame refresh.
Oh wait, CES is in a few days, maybe you'll be lucky afterall.
You appear to believe a couple of jumps on a bad day Mao did 7.7 rev per sec. On a good day, she probably can drill the ice in Vancouver and emerge, leg first, in Antartica.
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- Nov 12, 2009
I'm just going to say a few things. Is this 9.6 inches you speak of from the bottom of Mao's SKATES or the bottom of her FEET? The other thing is, if height is really a factor, Mao's height is about 4 inches taller with her skates on then without. So if she is 5'4" without her skates (and I've heard from people that she seems shorter than that in person) then she is about 5'8" with her skates which is a big difference. If the person who calculated the 9.6 inches wasn't consistent about measuring with or without the skates it could result in a false result. I tend to think Mao jumps more than 10 inches, but I can't really be sure. Caroline Zhang is about the same size as Mao and her jumps look no more than 4 inches off the ice.
TV? Never said it was done on a TV. It's all done numerically in software. And yes I have the BEST toys in my lab!
Oh-contrare. I am not claiming anyone else's numbers are right and I am not claiming they are wrong. You don't like my declining to definitively say someone else's numbers are right or wrong -- tough luck.
You are right in pointing out that it is vague where this statement was coming from.
I am a native speaker of Japanese and I personally assume from the context of this article that this quote was Ikegami's statement rephrased by the journalist. But it is possible that the journalist added some (possibly inaccurate) interpretation to Ikegami's theory in the way he rephrased it.
On the other hand, there is no direct reference to Ikegami in this particular statement and the passive voice is used. Therefore, it is also possible that the journalist is referring to someone else's theory.
To sum, I think that this statement can be read in either way ("It is said (by Ikegami)" or "It is said (by someone else) /"It is (generally) said...").
Some journalists send the researcher a proof before publishing their interview, but many others don't. So it is often possible that the researcher's work is misquoted or misinterpreted by the media.
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There is something seriously wrong with the camera here if that's the fastest spin ever recorded. The spin doesn't even blur.
hwell:It looks better in other links.
I do not know this prof, but his institution, Nagoya Univ, is one of the Seven Former Imperial Universities and the competition to get that position would be hard.
Besides, Mao's rink seems among the most scientifically advanced ones in the world. It has many facilities to enable scientific analysis. They built something extremely fancy for whatever reason.
That said, I would read his original articles in scientific peer-reviewed journals to know more about his theory because the ones reported in the media may not be accurate. We can just get a taste of it.
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I read through this thread and had a few thoughts.
Two skaters could be in the air for the same time and one jump higher than the other. All these equations assume the acceleration up = acceleration down. If the skater rises to the apex quicker they may spend 0.4 of the time going up and 0.6 of the time coming down right? But that is not the important part
Here is what matters:
I downloaded the 2009 WTT video that was referenced above. Deffinately a recent competition, I pulled the video into Kinovea (A free version of dartfish) Using the time line in Kinovea I can see that Mao is in the air for 0.73 sec.
I pulled some frames from that video and posted them here. There is no way she is only 10 inches off the ice. It looks more like 18. She looks about 10 inches in the second frame and goes at least another 8 inches up.
I too have seen Mao jump in person at practice sessions. She did a triple axel right in front of me while my elbows were on the boards. She was at least 18 inches off the ice. She was as tight as a pencil in the air, and when she landed there was barely a sound. It was truly and amazing jump.
Two skaters could be in the air for the same time and one jump higher than the other. All these equations assume the acceleration up = acceleration down. If the skater rises to the apex quicker they may spend 0.4 of the time going up and 0.6 of the time coming down right? But that is not the important part
Here is what matters:
I downloaded the 2009 WTT video that was referenced above. Deffinately a recent competition, I pulled the video into Kinovea (A free version of dartfish) Using the time line in Kinovea I can see that Mao is in the air for 0.73 sec.
I pulled some frames from that video and posted them here. There is no way she is only 10 inches off the ice. It looks more like 18. She looks about 10 inches in the second frame and goes at least another 8 inches up.
I too have seen Mao jump in person at practice sessions. She did a triple axel right in front of me while my elbows were on the boards. She was at least 18 inches off the ice. She was as tight as a pencil in the air, and when she landed there was barely a sound. It was truly and amazing jump.
BTW
I am not saying 18 inches is an extremely high 3A but Mao is not jumping 9-10 inches.
Tonya Harding and Midori Ito's were much higher. I think Harding was jumping like 36+ inches.
Mao is definitely tighter and faster in the air so there is merit to the article. I am just not comfortable with the numbers posted. I am not saying they are making the numbers up but 10 inches is not the typical Mao 3a. Either they caught a bad jump or they measured the time wrong.
I am not saying 18 inches is an extremely high 3A but Mao is not jumping 9-10 inches.
Tonya Harding and Midori Ito's were much higher. I think Harding was jumping like 36+ inches.
Mao is definitely tighter and faster in the air so there is merit to the article. I am just not comfortable with the numbers posted. I am not saying they are making the numbers up but 10 inches is not the typical Mao 3a. Either they caught a bad jump or they measured the time wrong.
Hurray
Finaly, a fact and not an opinion. 0.73 seconds is measured. That is 25.6 inches (65 cm) and an average rotation rate of 4.8 rotations per second. All making perfect sense.
Good Job!
now if you google him, it should be 2nd.
I wouldn't be surprised if he reads this forum. lol. This forum has a bunch of people who LOVE analytical discussion etc etc.
It would be cool if the discussions by skaters and serious skating fans here provide some hints in advancing scientific research in some ways, which may eventually help skaters advance their techniques.