Circumference or bottom of ball need to be on the line?

[FlyingBoat]

Do we judge whether the bottom of the ball touches the line to be in or use the circumference? If part of the ball is overhanging the line but not touching it, is it in or out?

I always thought it was circumference and called it that way, but seeing shot spot it looks like they are picking the bottom of the ball.

So if it is the bottom of the ball, do we need to judge how far it compressed when it hit? Or are we considering pretty much the middle of the ball needs to be on the edge of the line in order for it to be in?

 

[Timbo's hopeless slice]

If you can tell the difference, you are either playing 2.5 tennis or you should be a linesman at the US Open!

I think the rule is any part of the ball that contacts the line.

Surely if it is that close you just call the damn thing in and play it anyway?

 

[FlyingBoat]

To answer my own questions and as someone answered here, the ball needs to contact the line. Doing some reading, this is clear with clay tennis, where they look at the mark. It doesn't matter if the ball overhangs the line, the ball is out if the mark doesn't touch the line.

I can think of several situations where the ball is hit down the line, where you have a clear view and can tell if it touched or overhung the line. To the poster above, if you can't tell the difference between a half inch or so one way or the other on particular shots, then yes you should call them in. The rest of us who still have our eyesight should take it into consideration where appropriate.

I am not on a clay court often, but seeing the marks they make on TV, the mark is significantly smaller than the ball. Likewise with shot spot.

 

[Timbo's hopeless slice]

Yeah, we open players struggle with our eyes, you're quite right! Just as well we have umpires and linesman in most of our tournaments I guess...

Otherwise, I call the close ones in. If I can't see (with my limited eyesight, of course) a discernible gap between ball and line, it's in...

 

[user92626]

I actually think the whole outer line of the ball is considered once the ball lands. That's why hawk eye shows the mark size matching the size of the ball (a little elongated if the ball skids). If only the touching part is considered than the mark size is probably two thumb size.

Also, it's probably impossible for linespeople to see the part of the ball that actually touches the line. But they can see the whole outline of the ball and project it to the line, and through hawk eye dispute you can see that they can make call where a tiny part of the ball touches the edge of the line. No one disputes when almost half of the ball lands on the line, ie if you go by the bottom argument.

 

[SystemicAnomaly]

I believe that the ball contact area with the ground and not the "equator" of the ball is used to make an IN/OUT determination. A bounce event is only a few milliseconds in duration but the ball can compress quite a bit at times and often leave a large footprint (especially if the ball skids quite a bit). Some skidding footprints on clay are more elongated than those depicted by the Hawk-Eye system.

I've seen ball on strings collision captured with very high speed "film" where the ball compresses to about half of its diameter. I would expect the "equator" in such a collision also increases somewhat. Not all collisions with the ground will be a high speeds. However, a 120 mph serve can impact the ground at ~90 mph. I would expect the contact area with the ground to be significantly larger than a 20 mph collision for a ball with a similar trajectory.

The Hawk-Eye system may rarely ever capture an actual bounce event. The center of the ball, the ball position, ball trajectory and bounce location, and bounce mark are all calculated from information gathered from multiple high speed cameras. The bounce mark that we are shown by the Hawk-Eye system are a "virtual reality" approximation of the actual event. ITF testing of Hawk-Eye in 2006 showed an average error of 3.6 mm.

http://www.hawkeyeinnovations.co.uk/?page_id=1011

 

[LuckyR]

Do we judge whether the bottom of the ball touches the line to be in or use the circumference? If part of the ball is overhanging the line but not touching it, is it in or out?

I always thought it was circumference and called it that way, but seeing shot spot it looks like they are picking the bottom of the ball.

So if it is the bottom of the ball, do we need to judge how far it compressed when it hit? Or are we considering pretty much the middle of the ball needs to be on the edge of the line in order for it to be in?

You question is purely theoretical (assuming that you are not playing on clay). The reality is: if you can see court between the ball and the line it is "out", if you can't it is "in".

 

[Fuji]

I've always though it was the bottom of the ball, (The ball has to physically touch the line) for it to be in. Even on some of the hard courts I play on, some of the bigger serves leave marks on the surface, and it's pretty clear if they are in or out.

-Fuji

 

[mightyrick]

If it's that close, I always just call the ball good. The discipline is basically to be ready to hit the ball even if you think it is going to go out.

Don't be one of those people who literally watches the ball pass by them because they think it is going to go long by an inch or two.

 

[jswinf]

You question is purely theoretical (assuming that you are not playing on clay). The reality is: if you can see court between the ball and the line it is "out", if you can't it is "in".

That really is all you need to think about. I'd say that technically if any of the fuzz on the ball brushes any bump on the paint of the outside edge of the line, it's in. If a non-fuzzy ball drops (let's say from a high lob) next to the line and compresses so that its edge overhangs the line but there's no actual touch, it's not in.

But how're you gonna see that? Use your super-power to put the world on pause while you go kneel down and run the bounce back and forth a few times while you analyze it? I can imagine an engineer (no offense, engineers, just a for-instance) using that 'compressed ball overhanging the line but not actually touching it' line. Don't anybody do that, OK?

Just do like LuckyR says.

 

[Limpinhitter]

Do we judge whether the bottom of the ball touches the line to be in or use the circumference? If part of the ball is overhanging the line but not touching it, is it in or out?

I always thought it was circumference and called it that way, but seeing shot spot it looks like they are picking the bottom of the ball.

So if it is the bottom of the ball, do we need to judge how far it compressed when it hit? Or are we considering pretty much the middle of the ball needs to be on the edge of the line in order for it to be in?

The ball has to touch the line to be in. If part of the ball overhangs the line, but, no part touches the line, it is out.

 

[user92626]

SA,
For dropshots, passing shots where the ball bounces light and virtually not compressed at all, wouldn't Hawk eye show a smaller footprint?

Again, linespeople's vision is looking down. That means they'd see the whole ball overlaying the spot it lands. To see where the ball actually touches, they'd have to line up their eyes along the ground.

Probably the same concept is employed with footfault. Some shoes have the tip curving up and never actually touching the line, but does that matter?

 

[SystemicAnomaly]

SA,
For dropshots, passing shots where the ball bounces light and virtually not compressed at all, wouldn't Hawk eye show a smaller footprint?

Again, linespeople's vision is looking down. That means they'd see the whole ball overlaying the spot it lands. To see where the ball actually touches, they'd have to line up their eyes along the ground...

I've not seen any Hawk-Eye challenges on dropshots but I would expect the footprint to be smaller if the Hawk-Eye data and software is good enough to yield an accurate representation.

Linesppl are not really looking down. Usually they are sitting or lowering their body to get primarily a side view, not a bird's-eye view. Only the chair umpire is really looking down on the court.

 

[Squall Leonheart]

SA,
Probably the same concept is employed with footfault. Some shoes have the tip curving up and never actually touching the line, but does that matter?

The obvious problem with this is when players have their heels inside the baseline, but are still only touching the court outside of the baseline, like how Hewitt does.

 

[user92626]

The obvious problem with this is when players have their heels inside the baseline, but are still only touching the court outside of the baseline, like how Hewitt does.

That's my point. No part of Hewitt actually touches the baseline, but linespeople would still call footfault because his heel crosses the line.

 

[tes]

If it's that close, I always just call the ball good. The discipline is basically to be ready to hit the ball even if you think it is going to go out.

Don't be one of those people who literally watches the ball pass by them because they think it is going to go long by an inch or two.

After a long hiatus from tennis I have become one of those players who will let a ball go by because I think it will be out and it drops in by a foot. I do however make up for it by attempting to volley balls that are 4 feet out.

 

[mightyrick]

After a long hiatus from tennis I have become one of those players who will let a ball go by because I think it will be out and it drops in by a foot. I do however make up for it by attempting to volley balls that are 4 feet out.

LOL!

10char

 

[fuzz nation]

Aside from what happens in the theoretical realm and how the geometry of the court and the ball interact in my brain to come up with a call, I simply look for a chunk of green (or blue or whatever color the court is painted, etc.) between the ball and the line. If I don't see that, I can't call the ball out.

Even when a ball lands between my eye and the line behind it - maybe the service line when I'm receiving serve and the ball is just long - I can't make an "out" call on that ball unless it's deep enough for me to plainly see the space between the ball and the line.

I'd bet that my tiny brain is more swayed by the entire circumference of the ball than just the bottom that actually contacts the court. There's too much going on during competition for me to scrutinize the different portions of the ball. Since I only play unofficiated matches, I only make that "out" call when I'm sure that the ball is away from the line, so it's probably easiest to call that when the "belly" of the ball is away from the edge of the line. If it's overhanging the line without touching it, I just can't spot that.

One thing worth noting about clay courts is that you've got to make an immediate call, even though the ball pretty much always leaves a mark. Some folks get hung up on routinely checking those marks, but it's important to conduct the match the same as with any other surface. Either make an immediate call or play on. Otherwise it's likely that we'll get into too many of those "second chance" calls, which are described in the rules and the code.

 

[papa]

One thing worth noting about clay courts is that you've got to make an immediate call, even though the ball pretty much always leaves a mark. Some folks get hung up on routinely checking those marks, but it's important to conduct the match the same as with any other surface. Either make an immediate call or play on. Otherwise it's likely that we'll get into too many of those "second chance" calls, which are described in the rules and the code.

Well, I believe you'll discover the rules say "prompt" and not "immediate". Having a second bite of the apple certainly isn't though either so if one strikes the ball believing it "in" they really shouldn't then call it "out" if their shot goes astray. In the case of doubles, often partner is in a much better position to call the ball.

New balls generally, not always though, leave marks on hard courts - bit more difficult to see but they are there never-the-less. With older balls & older courts its difficult to tell.

Even on Har-Tru, calls can be difficult sometimes, especially if the ball strikes a nail head or skids on a line.

The general practice is that if you can't definitely call it "out" than its "in". In the case of doubles, if partners disagree on the call its "in" but not every call has to be verified by both - many times only one clearly sees the ball.

As most have already said, all it takes is one fiber of the ball to touch the line to be good/in. Has nothing to do with the diameter of the ball, its the footprint it leaves which depending on the shot can take on many shapes. When the ball skids, its footprint is not necessarily perfectly elongated either - can almost be a blunted end cone shape.

 

[ATP100]

Hawk-Eye is not for the players.

 

[West Coast Ace]

Don't be one of those people who literally watches the ball pass by them because they think it is going to go long by an inch or two.

+1. Never assume a ball is going out - especially true with the new poly strings that make the balls from heavy topspinners appear to 'drop out of the sky'.

SA,
For dropshots, passing shots where the ball bounces light and virtually not compressed at all, wouldn't Hawk eye show a smaller footprint?

It does. Because there is no 'skid'.

 

[user92626]

I'm not talking about skid. I'm asking that when the ball lands more straight down and easy, does Hawk Eye show the footprint the size of the quarter or the size of the ball's circumfernce?


Take a lob lands more or less straight down, Hawk Eye shows the spot the size of the ball circumference (and every mm of the spot is considered), does that mean the ball has to compress in half in order to actually touch the ground?

 

[fuzz nation]

Yeah, I know what you mean. I'm pretty sure that the mark that the Shot Spot/Hawkeye shows is the system's interpretation of the portion of the ball that touches the court, but not the entire diameter of the ball. A lob or a drop shot leaves more of a round mark because the ball isn't traveling much across the surface - that mark looks about the size of a quarter. A serve or ground stroke actually rolls and "smushes" along the court with a more glancing blow, so that contact mark is more oval shaped.

 

[papa]

I'm not talking about skid. I'm asking that when the ball lands more straight down and easy, does Hawk Eye show the footprint the size of the quarter or the size of the ball's circumfernce?


Take a lob lands more or less straight down, Hawk Eye shows the spot the size of the ball circumference (and every mm of the spot is considered), does that mean the ball has to compress in half in order to actually touch the ground?

FN's answer is very good here. Although I'm not connected with the "Hawk Eye" equipment or software, its my understanding that it takes into consideration the pace of the shot, height, spin, etc. From these variables plus know factors (weight, size and assuming a certain ball pressure), it can pretty accurately determine the path and mark the ball will leave on the court surface. I suspect that although there is some margin of error, its quite small. If I'm not mistaken, engineers from IBM were involved with its development.