Tennis Graphics -- Side View of Court and Shots

[TimeSpiral]

Hey, fellow TT'ers!

I'm presenting a high-ish-resolution profile image of a tennis court, drawn to scale (optimized for the web, not print)! In another thread, about moonballs, I said that I would start a new thread so we could discuss shot types. Apparently there is some disagreement about "clearance over the net" so one of the primary features of this graphic is a vertical net clearance ruler.

I self-publish tennis articles, and I have a fully featured article about this tennis court graphic, along with some of the examples, and some explanation. I'd love some TT feedback (because we love each other here). But, in case you don't want to be bothered with an article, I will post a link to the full sized image (it's big) and then paste in the lower-res examples.

Full Size Profile view of a tennis court, drawn to scale:
http://i.imgur.com/hxZgsvC.jpg

Here are the lower res examples from the article:

Heavy Topspin

First Serve

Well played slice

Heavy Topspin Moonball

The full sized graphic has a ton of features that hopefully the community can put to good use.

Enjoy and discuss!

 

[Mongolmike]

Thank you. Good stuff. And these graphics are taken from actual footage, or are they estimations?

 

[TimeSpiral]

Thank you. Good stuff. And these graphics are taken from actual footage, or are they estimations?

Thanks! They are estimations.

It's really difficult to get legit profile footage of these things. In the article I go into a little more detail about some of the considerations that went into the shot examples.

 

[Avles]

Few things...

-- Baseline not basline

--I suspect that the trajectory of the heavy topspin shot isn't accurate. I doubt that shots really plummet that dramatically due to topspin. I'll see if I can find some examples.

-- At risk of igniting another silly flamewar over semantics, 24 feet in the air seems really high to me. My guess (just a guess) is that most topspin lobs/moonballs are a lot lower than that, and that most shots that cross the net at that height arre defensive lobs.

 

[Avles]

All that said, it's a nice looking graphic and could be handy as a canvas for explaining and visualising shots.

 

[TimeSpiral]

Few things...

-- Baseline not basline

--I suspect that the trajectory of the heavy topspin shot isn't accurate. I doubt that shots really plummet that dramatically due to topspin. I'll see if I can find some examples.

-- At risk of igniting another silly flamewar over semantics, 24 feet in the air seems really high to me. My guess (just a guess) is that most topspin lobs/moonballs are a lot lower than that, and that most shots that cross the net at that height arre defensive lobs.

I can't believe I have to redo all those graphics because I misspelled baseline. FML. Thanks for noticing that!

You might be correct about the heavy topspin shot, but I doubt it's very far off. The Magnus Force will more effect the topspin shot later in the initial flight phase because the ball's velocity is slowing down. The topspin shot is not a clean parabolic curve, but one that dips towards the end of the flight phase. I would also like to point out that this is not a "standard" topspin groundy, or a "pro-level" groundy, but one player at our level, with a little bit of a high clearance, and a lot of spin. That ball definitely dives.

On your third point: gawd I wish you were right, lol! I've seen and played too many matches where my opponent is fully set up, and could easily hit a standard groundstroke, but instead launches a heavy topspin moonball 20 feet over the net. I wish I were being hypoerbolic, but that shot is definitely used. That's one of the reason for the low standing lights reference. In my last match my opponents regular groundstrokes were soaring at the same height as these lights, and sometimes even higher. It was literally absurd ... but so effective.

In my opinion, and this can be demonstrated by watching the pros, a good defensive lob can go forty to sixty feet in the air.

 

[Avles]

You might be correct about the heavy topspin shot, but I doubt it's very far off. The Magnus Force will more effect the topspin shot later in the initial flight phase because the ball's velocity is slowing down. The topspin shot is not a clean parabolic curve, but one that dips towards the end of the flight phase.

I know, the descent just seems a little dramatic to me.... Maybe if the ball began to drop a bit sooner?

Have you seen http://coronaperspectives.com/ ? It's a pretty neat visualization of ATP shot trajectories, though it took me a while to figure out how to separate out individual points. And I think that theymight have the matches mislabeled, oddly enough (what they call the London 2011 final looks like the Rome 2011 final to me). Worth a look, anway...

 

[TimeSpiral]

I know, the descent just seems a little dramatic to me.... Maybe if the ball began to drop a bit sooner?

Have you seen http://coronaperspectives.com/ ? It's a pretty neat visualization of ATP shot trajectories, though it took me a while to figure out how to separate out individual points. And I think that theymight have the matches mislabeled, oddly enough (what they call the London 2011 final looks like the Rome 2011 final to me). Worth a look, anway...

Super awesome! I've never seen that before. That's incredible.

Perhaps the drop is a little dramatic on the heavy topspin. Let me fiddle with it. Do we agree that the dip is more pronounced at the tail end of the flight phase?

 

[cjs]

You might be correct about the heavy topspin shot, but I doubt it's very far off. The Magnus Force will more effect the topspin shot later in the initial flight phase because the ball's velocity is slowing down. The topspin shot is not a clean parabolic curve, but one that dips towards the end of the flight phase. I would also like to point out that this is not a "standard" topspin groundy, or a "pro-level" groundy, but one player at our level, with a little bit of a high clearance, and a lot of spin. That ball definitely dives.

I think the pic is ok. In my opinion a really heavy top spin shot hit with both power and a bit of loop drops almost vertically before the ball bounce.

I hit my forehand this way and many opposition players who play me for the first time always misjudge baseline line calls. They think the ball is going to go well out and then it drops inside the line. Often they don't even play a shot expecting the ball to go out.

 

[TimeSpiral]

I think the pic is ok. In my opinion a really heavy top spin shot hit with both power and a bit of loop drops almost vertically before the ball bounce.

I hit my forehand this way and many opposition players who play me for the first time always misjudge baseline line calls. They think the ball is going to go well out and then it drops inside the line. Often they don't even play a shot expecting the ball to go out.

Yeah, I mean the pic certainly isn't describing all shots in that class. If it is off, I don't think it's badly off. Footage would probably help, but these are just crude mock-ups, not actual simulations, so I think they're performing their intended purpose fine.

 

[MasturB]

No way I can hit a 7 foot topspin shot unless it's a moon ball or I buggy whip it cross court to stay in the rally.

 

[toly]

Magnus Force

--I suspect that the trajectory of the heavy topspin shot isn't accurate. I doubt that shots really plummet that dramatically due to topspin. I'll see if I can find some examples.

Magnus force F is perpendicular to ball’s velocity Vb. When ball is rising F pushes ball downward and forward. The falling ball is pushed back and down. IMO it is possible the ball moves down vertically or even down and backwards. :shock:

 

[TimeSpiral]

Magnus force F is perpendicular to ball’s velocity Vb. When ball is rising F pushes ball downward and forward. The falling ball is pushed back and down. IMO it is possible the ball moves down vertically or even down and backwards. :shock:

^ Yep. No court, and no gravity, and a heavy topspin shot will create a spiral (because you suspected it could even move backwards). Although I suspect that conditions required to move a ball backwards would never exist in a game of tennis. The effect of the Magnus Force is so much easier to see when playing ping pong--even though the tennis ball will essentially do the same thing, just on a larger scale.

No way I can hit a 7 foot topspin shot unless it's a moon ball or I buggy whip it cross court to stay in the rally.

That's bizarre. Seven foot clearance is really not unusual at all. You see this sort of clearance all the time at the rec level, and you also see it regularly at the pro level.

 

[toly]

This is theoretical example of falling ball which moves backwards. Ball’s speed is 112mph, topspin 24055rpm. This is definitely unreal shot.

Sorry, that has nothing to do with OP. Your pictures are really nice, thanks.

Btw, you can get ball’s trajectories from TTW University calculator.

 

[Topspin Shot]

No realistic shot can curve backward due to topspin, but the theory is pretty awesome. Way to enlighten, Toly!

 

[toly]

No realistic shot can curve backward due to topspin, but the theory is pretty awesome. Way to enlighten, Toly!

OMG, at last you appreciate my work!!!???

 

[Topspin Shot]

OMG, at last you appreciate my work!!!???

I do!

 

[TimeSpiral]

This is theoretical example of falling ball which moves backwards. Ball’s speed is 112mph, topspin 24055rpm. This is definitely unreal shot.

Sorry, that has nothing to do with OP. Your pictures are really nice, thanks.

Btw, you can get ball’s trajectories from TTW University calculator.

Nice graphics! This is exactly the type of thing I was hoping to inspire: conversation, theory, shot trajectories, etc ... This came up because someone called into question my "heavy topspin" mark-up.

I know that they have a shot trajectory calculator, and while it might be more accurate based on the input variables, the input variables would be just as guessed as me using bezier curves in Photoshop to mark-up archetypical shot paths.

 

[toly]

Nice graphics! This is exactly the type of thing I was hoping to inspire: conversation, theory, shot trajectories, etc ... This came up because someone called into question my "heavy topspin" mark-up.

I know that they have a shot trajectory calculator, and while it might be more accurate based on the input variables, the input variables would be just as guessed as me using bezier curves in Photoshop to mark-up archetypical shot paths.

Do you know how to correct image optical illusion and photo camera distortion?
For example, in the picture below ball has too sharp downward trajectory. What can I do about that?

This is corresponding video. http://www.tennisplayer.net/public/site_tour/teaching_system_serve/index.html

 

[TimothyO]

I can't believe I have to redo all those graphics because I misspelled baseline. FML. Thanks for noticing that!r.

If you're going to redo them anyway, you might as well also redo them so the shot direction reads left to right since that's the natural way to read text/diagrams in the western world.

 

[WildVolley]

At the big tournaments the TV will sometimes show Shot Spot animations of actual ball flight and give the mph, etc. Obviously they've taken 3D measurements of hits for all the big players, but I don't know of a source for that data.

 

[TimeSpiral]

Do you know how to correct image optical illusion and photo camera distortion?
For example, in the picture below ball has too sharp downward trajectory. What can I do about that?

This is corresponding video. http://www.tennisplayer.net/public/site_tour/teaching_system_serve/index.html

Sorry, brother. I don't really understand the question. Can you rephrase it?

The video shows you what it captures, relative to its perspective. If you're look to extrapolate a 3-D model model from a 2D image or video (which is what it sounds like to me) you need to learn a technique called "3d camera matching" (sometimes called camera tracking, or match moving). Just a warning: it is extremely technical, and requires a detailed awareness of key input variables.

If you're going to redo them anyway, you might as well also redo them so the shot direction reads left to right since that's the natural way to read text/diagrams in the western world.

Who says you're the one hitting the shots in the diagrams? :twisted:

Kidding. Good suggestion, but not worth redoing them again.

At the big tournaments the TV will sometimes show Shot Spot animations of actual ball flight and give the mph, etc. Obviously they've taken 3D measurements of hits for all the big players, but I don't know of a source for that data.

The tournaments hire HawkEye operators, and that's how the information if gathered. Each tournament individually retains ownership over the data collected. There is no getting it without requesting a release of data, which I have not tried, but would imagine would be denied.

 

[toly]

I know that they have a shot trajectory calculator, and while it might be more accurate based on the input variables, the input variables would be just as guessed as me using bezier curves in Photoshop to mark-up archetypical shot paths.

Djokovic hits hard almost flat forehand.

This picture gives us some idea of how to get input variables for TTW University calculator. Here they are.

This is output picture.

 

[TimeSpiral]

Djokovic hits hard almost flat forehand.

This picture gives us some idea of how to get input variables for TTW University calculator. Here they are.

This is output picture.

Nice work! I would just amend it slightly:

In some instances, Djokovic hits hard almost flat forehand. This picture gives us some idea of how to get input variables for TTW University calculator, (but we don't know where he is on the court, or what type of shot is coming into his racquet.) Here they are.

​

I'm not a physics expert--hardly. But a little bit of searching revealed this document: Ball Trajectories, Factors Influencing the Flight of the Ball, by the University of Sydney.

The document really explains so many of the relevant physics at play: free fall, gravity, launch angles, RHS, RPM, drag, Magnus ... and provides technical formulas for everything. I wonder how accurate the TTWU is? I don't see the formulas published on their page. Either way, I'm sure it's pretty sufficient for what they're doing (comparing racquets).

Some really interesting stuff in that doc. Take a look!

 

[toly]

Nice work! I would just amend it slightly:

In some instances, Djokovic hits hard almost flat forehand. This picture gives us some idea of how to get input variables for TTW University calculator, (but we don't know where he is on the court, or what type of shot is coming into his racquet.) Here they are.​

You draw very nice picture of ball’s trajectories for different type of forehand/backhand, but the main next question is what exactly player should do to reproduce a particular trajectory. In physics this type of task is called the synthesis problem and that of cause much more difficult job than just drawing trajectory. By using TTW calculator we can play with input variables and find their optimum.

 

[TimeSpiral]

You draw very nice picture of ball’s trajectories for different type of forehand/backhand, but the main next question is what exactly player should do to reproduce a particular trajectory. In physics this type of task is called the synthesis problem and that of cause much more difficult job than just drawing trajectory. By using TTW calculator we can play with input variables and find their optimum.

See my above post, I just appended it.

I see where you're going now, and that's an interesting observation! The primary graphic, which I will paste below, is designed to be a profile to scale canvas to be used to approximate ball height, bounce, and vertical court position relative to the flight path. Court position is such a big deal at the rec-level.

I was hoping to provide the community with a resource that they can experiment with, and really do anything with. Unfortunately, so far, the article is getting extremely low exposure (less than 50 views :shock. Oh well. I suppose it will be a matter of time, whether or not people vote for these articles (with links).