I've updated the thread with results for some of the Olympics ladies SP. I've only gotten through the first 9 so far (in order of how they scored in the free skate). Overall the video was pretty good quality since it was 25 FPS interlaced, so I was able to extract the individual frames via Avidemux and effectively view it at 50 FPS (albeit at half the resolution). The replays, when usable, were often at 1/3 the speed so those jumps were analyzed at 150 FPS which is, needless to say, very good.
The jump layouts in the different SP's were fairly similar to each other (probably due to requirements), so they allow for a better direct comparison between the different skaters.
finally, read this thread, that was amazing work. One good way to judge under-rotation, is to look at the ice tracing, kinda hard if you only have broadcast footage,if by chance, you got the photos of skater's ice tracing, or a good close-up, then you can draw a tangent line at both the curve of take-off edge and landing edge, and measure what is the degree of the angle between these 2 tangent lines.
I intend to do some examples here, but kinda lousy at edit photos, I will try.
think about this method, it is kinda hard to determine pre-rotation...
Well when I get around to rotation it will be by directly looking at the skates in the video. But yes, the ice tracing can give some pretty good measurements, when available. However, there's some stipulations to this:
1. According to these forums, the way to measure pre-rotation and under-rotation is by the skate position at the time the skate leaves the ice and hits the ice. Usually, on takeoff a skater will rise up onto the toe pick, and then the skate will continue rotating on the toe pick before it leaves the ice. Similarly, on landing usually the skater will land on the toe pick first, then continue rotating until the edge touches the ice, at which point the skater begins traveling to generate the tracing. Thus, the tracing only measures the angle of the edge when it was moving, not the actual position of the skate at the moment of takeoff and landing.
2. One way to use the tracing to see an under-rotation is to look for a "hook" or really small curve at the landing tracing. However, this only shows that there was definitely an under-rotation; if there isn't one, you still don't really know if the jump was under-rotated or not.
3. For an edge jump (salchow, loop, axel), it's fairly easy to assume the flight path is from the end of the takeoff tracing to the beginning of the landing tracing. However, I'm not sure what the flight path should be assumed to be for a toe jump, however, because there's the edge tracing as well as a divot for the toe pick. Should the end of the edge tracing, the toe pick divot, or the midpoint between them be considered as the starting point for the flight path? This is actually a general question for when I get around to measuring jump rotations.
Vanshilar maybe you can also do Patrick and SoYoun's jump height too. SoYoun seems got very big jumps. and Patrick's data perhaps is very useful when compare to Yuzuru to study the efficiency/economy of jumps.
also from your data, Yuna's both lutz are of equal height, therefore her tight landing in her second lutz is indeed caused by a slight tilt of body axis in the air. Air position could be a factor that affect jump landings as well. maybe by study that, we can find out how skaters without perfect air positions managed to land their jumps.
also can you do Mirai's jump height as well, and figure out, what really is the cause of her under-rotation, height? or others.
I'll get around to SoYoun's jumps in a bit. However, what do you recommend for Patrick's and Yuzuru's data? I'm wary of using the Olympics for that because it was such a splatfest so I don't think it's as representative of their abilities. Is there another event where the video is readily available (and hopefully good quality) for them? Similarly, what are some good events for Mirai?
I should note that jump height is only one component of a successful jump. There's also rotational (angular) momentum, or how much rotation or spin energy (actually, momentum) the skater can generate when taking off; moment of inertia, or how tightly the skater can straighten their body in the air to spin more quickly; snap time, or how long it takes the skater to transition from their takeoff position into their back scratch position in the air; and other factors like the amount of tilt (both perpendicular to the flight path and in the direction of the flight path) in the axis of rotation as they spin in the air. So I don't think it will just be an easy one-solution thing; her coaches most likely have done a lot more in-depth analysis of her jump technique and would have fixed it already if it were so easy.
Based on what they actually presented in the programs and how the judges would have judged cumulatively, taking all jumps with a BV greater or equal to 2A,
I forgot about using fancam video. That definitely is possible, though I do wonder about how much the camera angle might complicate things, as well as the size variation between rinks (aren't Asian rinks often a bit bigger?). For speed into the jump, would you be looking more for the glide speed going in or the speed retained up to takeoff? On some jumps a lot of speed is lost during the jump entry.
