Just a bit dissapointed -- Sim Golf will never be "real"

[GMR]

Hi All,

So after having wanted a golf sim for a very long time now, I finally took the plunge and bought a skytrak a couple weeks back. I used to play regularly in an indoor league on AboutGolf simulators so I was pretty familiar with all the positives and negatives of simulator golf, and was very excited about using the Skytrak to improve my game. I aologise if this comes across as overly negative, as that's not really my intent, but despite being very familiar with indoor golf I've discovered something that I wish I had known before I bought my setup. Not that I wouldn't have done exactly the same, but I just feel like I didn't have the full picture before making the plunge.

So the first thing I will say is I'm actually very impressed by the unit itself. For the cost, I think that the data I'm getting out of it is of extremely high quality. I will happily say that it is absolutely hands-down an improvement on the AboutGolf monitor. First of all the flexibility to use your own balls--and get reasonably accurate spin data doing so--is HUGE, as the AboutGolf makes you use these ridiculous marked balls that don't really spin and, as I found out, are actually lighter than real balls and are therefore subject to crack while using them... Also I think to compensate to the non-real balls, the ball flight model in the AboutGolf is really wonky and would always give me very unrealistic ball trajectories, even if the eventual carry distance was somewhere near correct.

With the Skytrak I really don't doubt the veracity of the data I'm getting at all. Ball speeds, trajectories, mishits--everything seems on point. I'm punished for bad shots and good shots go just about how I'd expect them to. Just about.

So last night I decided to really dig into my numbers and see how I stacked up. Fortunately, my ball speeds are actually pretty much in line with the PGA tour average, so it's a pretty apples-to-apples comparison vs the published Trackman charts showing tour averages by club. Going through my #s club by club, I was pleasantly surprised to see things pretty much in line in terms of ball speeds, but the two numbers that jumped out to me were 1) launch angle and 2) spin rate.

For every club I hit, my launch angle was consistently 2-3* higher than the tour average. Interesting, I thought, but hey I can buy it because we know a number of those guys use a lot of shaft lean to really deloft the clubs and hit them further. But wait...why are my carry distances then actually slightly FURTHER than theirs (e.g. 7i: 180yds vs 172yds, 5i: 204yds vs 194yds, 3h: 231yds vs 225yds)? This is in the standard Skytrak range with altitude set to 0 and no silly boosts on, and ball speeds pretty much in line, so shouldn't be any funky business with the calculations.

Then I noticed the spin. A good 750-1,500 lower than tour average with every club. Before you ask this is using virutually brand new premium balls (Srixon Z Star). OK well I play clubs with shafts that are really stiff--almost on the border of being too stiff for me--so it would make sense that I might have lower spin numbers. But unless I'm just very shallow into the ball (which I never have been) those launch angles and those spin numbers just weren't adding up. If you add to that that I tend to be a low-mid trajectory guy on the course, and these numbers would imply I'm hitting high flat moonballs (110ft peak height roughly according to the flightscope trajectory optimiser), something just wasn't right.

That's when I found this article: https://blog.trackmangolf.com/mats-v...ts-difference/

Turns out the numbers I'm getting from the Skytrak are most likely, as I imagined, on point. Wouldn't have mattered if I had bought a GC2, Trackman, or any other contraption that measures ball data... The numbers were wrong because the ball flight was wrong, because I was hitting off a mat instead of grass. Basically every time I hit the ball off my Fiberbuilt mat, it's as if I'm hitting from a flyer lie in the rough. Which is great if you want to practice hitting from flyer lies, but not so great if you want to get a precise view on your "stock" distances and ballflight from the fairway.

So that's really it. I know it's a bit nitpicky, but I was really excited to really dial in my distances using my real clubs and my real balls all winter in my newly built mancave. And while the Skytrak will still provide me some great feedback and will still be tons of fun to play with, that level of precision that I was hoping for in terms of "real" data just isn't going to happen, which makes me just a little bit sad.

Thanks if you managed to make it this far, and will welcome your feedback.

[GMR]

Thanks for the suggestions. Think what I really need to do is find a way to take the skytrak outdoors and get some good data to use as a reference, and then figure out how to tweak things indoor to get me close--rather that means getting a softer higher-spinning ball, or tweaking software settings, or whatever.

Fortunately my house backs up to a golf course so there is a hole I can hit real balls in the evening when it's quiet to get some data. Unfortunately, however, every time I have tried to use the Skytrak so far outdoors on real grass it fails to pick up even a single shot... Any suggestions on how to help it get a reading hitting off a real fairway?

[GMR]

I also agree that there should be testing done on various mat types that shows the differences in launch data off all different types of mats, and that it should be pinned somewhere in this forum. When I was researching mats most of what I went off was people's anecdotal experience ("this mat hurt me when I started hitting too many balls," "I love the fiberbuilt--get much more real distances hitting off it!" "my truestrike wore out after two weeks," etc.). Like I said in my OP I actually had a decent amount of experience with indoor golf so thought I knew what to expect, but the one thing I wish I had known was the effect the mat makes on the launch conditions...may have spent some more time testing mats before I made a decision. And I may have picked the same one, but at least I would have been more aware of any tradeoffs I might have been making.

[GMR]

https://proputtsystems.com/which-true-strike-do-i-need/ - Interesting that you say the Truestrike gives you the best data compared to real turf. In the linked example they only show their mat vs a turf mat...

I would be interested to see turf vs Fiberbuilt vs Truestrike vs Divot action. If anybody has all three of these mats and would do some non biased testing that would be really cool

This an interesting article, and they definitely acknowledge the issue of getting longer carry distances with normal mats. However they also state the following, which I believe has been proven to be fals through high-speed camera analysis:

"This downward strike is what causes spin because the ball will pinch between the clubface and the turf below, subsequently traveling out and up."

So maybe the truestrike works better than most (haven't tried it so wouldn't know), but still looking for a valid scientific explanation as to WHY a mat should even affect launch angle and/or ball spin in the first place. Any thoughts?

[PercyDalton]

I would imagine with deeper bristles the club can travel further down without resistance and the ball connects higher on the club face

[Warpdave]

I don't see how the Matt affects spin when properly struck.
Watching in slow motion, I see no "pinch". I see the ball launching up off of the club face.

https://youtu.be/OStvJf9qdUA

[inorkuo]

i was under the impression that there is no pinching as well but this thread has got me thinking that there has to be some ball/turf interaction. otherwise, it wouldn't matter what we hit off of. now take a look at the video Warpdave posted above. at 0:24, pause it right before the club hits the ball and hit the period key to go frame by frame. you'll see the tee push further into the ground as the ball deforms. i think that's pretty definitive proof that the ball pushes into the ground at impact.

[GMR]

I can only think of three ways it's even possible that a firm hitting surface would make a difference given ball-first contact:

1) There is some degree of turf interaction between the ball and the ground at the time of impact. On a fairway lie this somehow causes the ball to compress differently than it would on a tee, imparting more spin to the ball...

2) As the club makes contact with the ground while still in contact with the ground, there is a small amount of gear effect that causes the fact to rotate and impart the lower launch and increase the spin. Would have to think that if this were the case a very firm mat like the CCE would have a lower launch angle though (which according to the TM article it does not)

or

3) The club actually enters the ground the smallest fraction of a second before striking the ball. On a grass lie the ball is "sitting down," while on a mat like the fiberbuilt the firm fibers prop the ball up just a touch causing the ball to come off the face a groove or two higher, thus the higher launch and less spin. This may actually be most likely as it would explain why the ball tends to come off very low and with a lot of spin when hitting off hard-pan lies (ever tried hitting off a cart path?)


Incidentally, any three of these scenarios being true would indicate that a ball should launch higher and when less spin when hit off a tee...

[inorkuo]

here's my theory. the fiberbuilt fibers are much stiffer than fairway grass. when the ball is compressed on the club face, it deforms and becomes an oval. on turf the center of the ball stays at the same level as the bottom of the ball pushes into the fairway grass. on fiberbuilt, the bottom of the ball can't push through the stiff fibers and the center of the ball rises slightly causing the ball to come off a groove higher.

[GMR]

Interesting thought but that wouldn't explain hardpan lies. After all, the cart path is much stiffer than either a mat or the fairway, and shots from asphalt will launch VERY low and with a LOT of spin. Compare that to shots off a tee that will launch more like the mat--higher launch and less spin. Maybe the "pinching" does actually occur somewhat, but it's not the ball being pushed down into the ground as much as it is the ball being unable to fully deform into an oval due to the firm ground below the ball preventing it.

If this is true, it would also indicate that a) the launch and spin of low-compression balls should theoretically be more sensitive to the lie type than high-compression balls and that b) higher-speed players will notice a bigger discrepancy between tee/mat strikes and firm fairway or hardpan strikes.

Lots of hypotheses to test!

[Mike90210]

https://www.youtube.com/watch?v=_DBD_3rfKVs - This video shows the club/turf interaction slowmo for the Fiberbuilt. Shows the club hitting the fiberbuilt grass before the ball.

I think that one of the biggest issues with repeated striking from mats is that the golfer actually changes their swing when hitting off of a mat compared to real grass. Even if they don't consciously mean to, it's different than actually playing a round.

Someone would really have to test all of these mats to see, many manufactures may distort results on websites. I think mats are more important that previously thought especially since indoor golf is getting massive

[Snaphook]

When playing golf i do see a lot more spin in dry conditions than wet, even with a dry ball. Also you usually get a lot more spin from fairway bunkers.
Playing par 3:s i tee up if it.s into the wind or i need some extra carry as i feel that it spins less that way. If i want more spin i look for a hard dry patch to hit from.
These are only my experiences and might be because of some faulty way i strike the ball, but it works for me.
All of the above seems to indicate that there is some interaction between the ground and the ball.
Spray some water on the mat and hit a dry ball, the spin will come down a lot.

[Snaphook]

Actually when think about it, the trustrike seems to have more friction than the cce mat.
Maybe i should tape some sandpaper on my mat and see what happens. I do think it will show more spin?

[GMR]

Good question... let us know if you decide to go through with that experiment!

[Ronsc1985]

Elementary physics shows that any golf shot hit with a face that has a positive angle relative to the ground on contact with the ball causes the ball to go up. Contrary to what you may hear on TV during tournament broadcasts and/or golf instruction shows the ball is not pinched between the clubface and the ground on any shot not topped.

The interaction of the clubhead with the ground is another story if you do not contact the ball first.

The other factor is what gets between the clubface and the ball. Anything that lowers the coefficient of friction between ball and clubface decreases spin and increases launch angle relative to the clubface. Grass, moisture, mat fibers etc. influence the above.

Different mats have varying influence on the above. Hit the ball first and there is not much difference. Don't and you get what you get.

I would point out that the mat is the same day to day, The golf course turf/lie etc.isn't so comparing mat with course is not one to one as the course turf/lie etc. are variable while the mat is not.

[GMR]

Yes that has always been my understanding as well in terms of no pinching, etc. But I cannot then for the life of me understand why off a firm mat like the fiberbuilt, where the ball sits up nicely and there is very clearly nothing between the ball and clubface at impact, why launch should be increased and spin decreased. And I know it's not because I'm hitting ground first--my miss is very much thin not fat, and I'm fairly positive the ball speeds I'm getting would be impossible for my swing speed given anything but a near-perfect strike.

I also get the same higher-launch lower-spin flight hitting irons off tees. That may be a matter of catching it a touch higher on the face granted, but clearly nothing between ball and clubface there. Why then would a fairway lie result in a lower launch and higher spin?

I'm thinking the answer must be that the club-ground interaction on a mat somehow differs from that on a fairway and results in the ball coming off a groove higher, much like it does when hitting from a tee. Just can't really figure out what exactly would happen to cause that...

[Ronsc1985]

I also get the same higher-launch lower-spin flight hitting irons off tees. That may be a matter of catching it a touch higher on the face granted, but clearly nothing between ball and clubface there. Why then would a fairway lie result in a lower launch and higher spin?

I'm thinking the answer must be that the club-ground interaction on a mat somehow differs from that on a fairway and results in the ball coming off a groove higher, much like it does when hitting from a tee. Just can't really figure out what exactly would happen to cause that...

Chances are when hitting from a tee you have a more positive clubface angle from hitting up slightly or down less then on a fairway. With respect to a Skytrac you also have to take into account the error tolerance of the readings. Skytrac and Foresight publish theirs, the radar units not so much.

Some people say the clubhead bangs into the mat while the ball is still on the clubface. Since the ball is on the clubface for about 0.5 milliseconds any meaningful effect from this would seem to be a stretch.

In summary there are too many variables hitting outdoors to achieve the small differences that are bothering you. This plus the variability of anyone's swing shot to shot makes one to one comparisons impossible. Even tour players seldom get the ball to the desired distance for anything but pitch shots and they have every blade of grass/slope/distance etc. previously measured. If they did scores in the vicinity of 54 or so would be common.

[GMR]

Chances are when hitting from a tee you have a more positive clubface angle from hitting up slightly or down less then on a fairway. With respect to a Skytrac you also have to take into account the error tolerance of the readings. Skytrac and Foresight publish theirs, the radar units not so much.

Some people say the clubhead bangs into the mat while the ball is still on the clubface. Since the ball is on the clubface for about 0.5 milliseconds any meaningful effect from this would seem to be a stretch.

In summary there are too many variables hitting outdoors to achieve the small differences that are bothering you. This plus the variability of anyone's swing shot to shot makes one to one comparisons impossible. Even tour players seldom get the ball to the desired distance for anything but pitch shots and they have every blade of grass/slope/distance etc. previously measured. If they did scores in the vicinity of 54 or so would be common.

Sorry but have to disagree here. It it were a few yards then it would be clearly inside the margin of error and that would be one thing. But I'm literally getting about 10-12 yards more carry distance with my 7i, which goes up with each subsequent iron to a max of about 15-20 off my 3h. Sorry to say but that makes it really hard to work on distance control, which is half the reason I wanted the Skytrak in the first place. And again, I am confident it is not the unit, but the mat which is causing the discrepancy, as the readings for ball speed, spin, and launch angle are all shockingly consistent on well struck shots.

[Ronsc1985]

Sorry but have to disagree here. It it were a few yards then it would be clearly inside the margin of error and that would be one thing. But I'm literally getting about 10-12 yards more carry distance with my 7i, which goes up with each subsequent iron to a max of about 15-20 off my 3h. Sorry to say but that makes it really hard to work on distance control, which is half the reason I wanted the Skytrak in the first place. And again, I am confident it is not the unit, but the mat which is causing the discrepancy, as the readings for ball speed, spin, and launch angle are all shockingly consistent on well struck shots.

You might try computing the actual distance error instead of guessing about what error the tolerances of a Skytrac can produce. You might also try a different mat. I have a CCE elite and the distances/spin etc. are what I see for the same ambient conditions on the range which has flat lies.

The course I most often play has Zoysia fairways and a CCE mat has somewhat similar characteristics in that if I hit it even slightly fat the distance goes down as does the spin. It also never bothers my elbows, wrists etc. although I have graphite shafts as steel shafts even on the course eventually give me joint pain.

Aside from all that I really don't understand your problem. If as you claim you know what the mat vs course differences are just subtract the differential.

I have never used a Skytrac although I did have a Vector Pro for a few years which used the same method of ball flight characteristics i.e two pictures separated by a fixed time interval. In the Vector Pro case it had to have a line on the ball or long thin logo the vision software could detect to measure angular rotation during the fixed time interval, I now have a GC2 which uses an entirely different method of image capture, thus it's much better error tolerance and much less picky ball placement requirements.

[Clevited]

I have been contemplating this "mat behavior" for some time, and due to another thread, it got me thinking about it again and I thought I would post on this one.

Here are 2 assumptions I made before I get to what I think happens.

1) Mats are typically softer than what I would say the fairway lie they try to emulate is.
2) Mats are typcially higher friction than the fairway lie they try to emulate is (water content of grass I think causes the substantially lower friction).

What I think happens as simple as I can put it:

Fairways are typically firmer than the mats that try to emulate them. When a ball is struck with a decending blow, the ground will feel some of that force and deform a small amount before directing that force back into the golf ball and therefore back into the club. The amount of deformation, I feel, has a direct impact on how much friction the ball will have with the club face. More deformation, the ball will have less force over time exerted onto the clubface, it will then slide up the club face further, it will spin less due to less friction and it will launch higher due to likely taking off above the club's center of gravity. Less deformation, the ball will have more force over time exerted onto the clubface, it will slide up the club face less, it will spin more due to more friction and it will launch lower due to likely taking off below the club's center of gravity.

Mat friction also has a role in this I think. Some mats have higher friction than a typical fairway lie and some have similar or maybe less. I envision a mat with high friction might sort of wrap itself around the ball when its struck and grab hold of it ever so slightly. This would, in my mind, decrease spin even further due to the grabbing not letting the ball turn, but certainly letting it slide up the face.

Mat friction and firmness would play an even bigger role for someone who hits fat, even if its only very slightly. On a typical fairway, a person might easily get away with a very slightly fat strike, maybe not even notice it due to low friction of grass and the firmness of the fairway. The same strike on a mat, I feel, could cause some very noticeable effects. Slightly fat strikes on a mat can, in my mind, slow down your club speed significantly, turn your club a little open, depress the mat enough to make the ball strike higher on the club and make for a potentially weak high fade shot.

This is all just how I make sense of it. Feel free to point out any incorrect physics concepts or what have you lol.

[shimonko]

Agree on a lot of your points there. The divot action clone I'm finding is definitely catching the sole and letting the toe race pace the heel. Pulls galore, lower launch. Check out https://youtu.be/PfwHqgseOuw?t=10 - this is a 2-iron, perfect strike, I just can't see the grass having any significant effect here. The ball is tied up a touch however as opposed to nestling down in a mat which - a fiberbuilt it probably relatively sinks quite a bit. Grass density is also a lot less in real life - you get a few blades as opposed to a dense wall.

[shimonko]

Good post, GMR. However PGA Tour averages do not necessarily apply to any one tour player. For example, a player with the average launch angle does not necessarily have the average ball spin. A better test would be to find a PGA player who has similar ball speed to you. And of course, 7-iron's aren't 7-irons - there's no standard 7-iron loft manufacturers must obey, deflofting through impact as you mention and changing static loft for gapping. Again you're comparing your 7-iron versus the average.

That doesn't however invalidate your suspicions and the Trackman article is good in that they used a +2 marker. I would prefer to see photographic evidence though, at least of launch angle.

I find I get a lot spin off my mats (a hard driving range mat and a divot action clone) - painfully so. If I get time this weekend, I might capture some ball launches from grass and range mat with both a SkyTrak and high speed camera.