> Also, the watch presumably can't tell how fast the ball is served, which depends on the racquet speed and whether you make good contact with the ball.
I think I disagree here. It should be possible to build a model that infers things like racquet speed and where the ball made contact with the racquet based on accelerometer data. At the end of the day you have an arm attached to a racket moving at some speed, that impacts a ball that is relatively not moving.
A straightforward model could calculate the lost momentum in the arm + racquet, assume the ball's mass, and work backwards to the ball's velocity from there. I'm assuming there is more ML magic behind Apple's implementation though.
I would look into this more. I was watching the French Open just yesterday and I heard Darren Cahill say that top juniors now a days have the technology so that when they walk off the court it will tell them what strategy worked what percentage of the time and what they should have been doing more. Pretty interesting comment, although they never did show an example of it I totally believe it. Babolat[0] pure drive meets Sony[1] racket sensor.
The only project I ever built with an Arduino is a wristband with a piezo sensor and it counts the number of balls I hit while was practicing. I thought about expanding it more, but that was the only data point I was really interested in.
You're right that it's not possible to react if all the information you have is the trajectory of the ball after it leaves the racquet. Good players will subconciously be predetermining the path of the ball by looking at how the opponent is striking the ball.
Until you realize your standing-up-arm-waving strategy is being destroyed by the person sitting on the couch making little wrist flicks, who may as well be pushing buttons for all the motion they're making. And that person isn't experiencing severe RSI, the likes of which doesn't happen playing those sports for real, 5 minutes into the match.
Interesting from a gadget standpoint - I wonder if any "regular" tennis players will be interested. I am reminded of this very clever lean startup experiment about a similar concept (though it was in the racquet, not a wearable).
As a tennis player, I think this is super impressive.
Their models actually do a decent job of replicating true tennis strategy, and as they pointed out, even account for the quirks like the left handedness of Nadal.
However, it's still a bit unrealistic due to the lack of full data.
There's 3 things that make a tennis shot what it is: placement (covered in the video), pace (speed of ball), and spin (rpm and direction of spin). In this method, they only use placement. Probably because pace and spin data don't exist at this scale.
But there's a big difference between a slice, flat, and top spin shot to the same placement on the court, and it directly affects the return shot. For example, it's a very common and 'safe' play to return a slice with a slice
This is awesome. I am really looking forward to the sensor technology moving forward and how the world will change when everything begins to be measured.
I just purchased a Babolat Play racket which tracks every shot you hit when playing tennis. For the first iteration, its very impressive. To walk over during a water break and see the longest rally and stuff is pretty cool. Plus, different players definitely bring up completely different stats, which is also good to see. The future for tennis I suspect is something like playsight[0], which is cameras and a base station that can record you play, give you live serve mph, and even call the lines. But for now, the Play is the most amazing thing to happen tennis. 1662 balls hit this week.
I agree that the stats don't provide insight regarding game play and strategy. IBM has been providing the same weak stats for years now. I would like to see tennis incorporate the hawk-eye system tracking player movement and shot placement as well. Perhaps that could produce a heat map. On that note they can also eliminate the line judges while we're at it. The whole challenge system is idiotic. They have the tech, they should incorporate it throughout the sport.
> For example, a professional tennis player can follow the trajectory of a tennis ball after it is served at a speed as high as 160 miles per hour, move to the optimal spot on the court, position his or her arm, and swing the racket to return the ball in the opponent’s court, all within a few hundred milliseconds.
I suspect if you made a perfectly invisible ball, you'd find people would manage to hit it back quite often. There's a lot of signal from the opponent's body motion.
Didn't look at the article, but I was disappointed that Wimbledon doesn't have automated line calls. Most atp/wta tournaments above a certain level have no line judges these days.
"a professional tennis player can follow the trajectory of a tennis ball after it is served at a speed as high as 160 miles per hour"
This is false or at least highly misleading. A reader might imagine that the player's eyes track the ball in flight. This is not what happens. A pro player reads the position of the serve and begins moving before the ball is hit. The predictive power of the brain is much more important than the speed and precision the author was trying to highlight here.
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