TrackMan article - difference between hitting off mat and grass

[JBones 1,237]

Very interesting article by TrackMan on the differences between hitting off a mat and hitting of grass.  I always knew hitting off mats can give you some crazy distances (yesterday FlightScope was telling me I was hitting my 7i 220), but I didn't realize the dispersion would be that far off.  Give it a read. 

Mats vs Grass - What's The Difference? Master study by Ryan Johnson & Greg Mathewson. http://t.co/EWKefXkWu2 pic.twitter.com/vyxaQuKocu

— TrackMan Golf (@TrackManGolf) November 26, 2014

[JBones 1,237]

Something interesting that I have to add here.  I don't know the science between how LMs work, I know they measure variables and do calculations to give you the data that you see.  I got on the FlightScope yesterday with my cousin to do some theory testing for a thread (unfortunately the data was garbage....a carry distance of 224 on a drive that was 123 SS, 1.48 smash, 15.4* launch, and 1854 rpm spin...it was like that on all woods) and we got some pretty conflicting data.  We were trying to guess distances with a 7i, for the swing we were putting on it, my cousin was up first..."3/4 swing, 165", he hits it 163; three times in a row the same swing netted between 163-167.  I step up "3/4 swing 178", it goes 210, then 213, then 220.  My cousin gets back up "full swing, should be around 175", 5 of them were between 175-180.  I step up "full swing SHOULD be around 190", first one goes 223; now I just want to see how far I can hit my 7i on this thing, so I take a rip...106 SS 238 carry.  We start hitting a PW, again my cousins distance is spot on, mine.....190.  We have done this on multiple occasions on multiple platforms (TrackMan, FlightScop, etc) and get the same results, he is spot on, mine are crazy long.  Why is that?  Somebody with a lot more knowledge than I will have to answer that.

[GolfSpy Barbajo 9,600]

This little nugget was especially interesting:

 

"Seeing a 2.7* lower launch off of grass did grab our attention. For instance during an iron fitting we would like to see 2* Launch Angle change between irons, i.e. from 6 to 7 iron. So if we do not know this information as to how grass will affect the golf ball, a perfectly fit 6 iron off of the mat will launch like a 5 iron on grass. This type of change can result in properly fit golf equipment off a mat, but will not achieve the desired Launch Angle when hit off grass."

 

The near 2,000 RPM difference in spin was kinda fascinating, too....

 

Is the moral of the story to get fit on grass?  Or make sure your fitter takes this info into consideration?

[MmmmmmBuddy 1,570]

Something interesting that I have to add here.  I don't know the science between how LMs work, I know they measure variables and do calculations to give you the data that you see.  I got on the FlightScope yesterday with my cousin to do some theory testing for a thread (unfortunately the data was garbage....a carry distance of 224 on a drive that was 123 SS, 1.48 smash, 15.4* launch, and 1854 rpm spin...it was like that on all woods) and we got some pretty conflicting data.  We were trying to guess distances with a 7i, for the swing we were putting on it, my cousin was up first..."3/4 swing, 165", he hits it 163; three times in a row the same swing netted between 163-167.  I step up "3/4 swing 178", it goes 210, then 213, then 220.  My cousin gets back up "full swing, should be around 175", 5 of them were between 175-180.  I step up "full swing SHOULD be around 190", first one goes 223; now I just want to see how far I can hit my 7i on this thing, so I take a rip...106 SS 238 carry.  We start hitting a PW, again my cousins distance is spot on, mine.....190.  We have done this on multiple occasions on multiple platforms (TrackMan, FlightScop, etc) and get the same results, he is spot on, mine are crazy long.  Why is that?  Somebody with a lot more knowledge than I will have to answer that.

 

 

Spin rate.. All about the spin rate.. For a high speed player (Like yourself) it is very normal for LM numbers with irons to read extremely long due to the low, almost driver like, spin numbers. Next time you are on the monitor, check the spin #'s...

[JBones 1,237]

Spin rate.. All about the spin rate.. For a high speed player (Like yourself) it is very normal for LM numbers with irons to read extremely long due to the low, almost driver like, spin numbers. Next time you are on the monitor, check the spin #'s...

 

I'm not a low spin guy.  I can't tell you exactly what they were, but they were quite a bit higher than my cousin, launch angle was also higher.  When I was getting fit for my current irons on the TrackMan it was giving me long distances with spin and launch angles that were "perfect" for the irons I was hitting.  I will get more data my next go around.

[revkev 25,442]

Regardless of what sort of "spin" you put on it this is very interesting stuff.  Clearly grass introduces an entirely new set of variables that aren't present with mats or rather the mat removes variables that are present when one is hitting golf shots on a real golf course.

 

I think anyone who plays/practices a lot knows this from experience its just that we weren't aware of the extent of the differences that grass/mat made.  Now we know. 

 

Thanks Bones

[markb 244]

I've long disliked monitor sessions indoors off of mats.   I think they are garbage, but this may just be that I am twitchy and can't adjust to the conditions.   My wood swing is always off, I'm always afraid of hitting something in the backswing.  They often show me with big sweeping hooks that I don't hit in real life.  Plus I'm a digger with my irons, so a mat always saves every swing and I can thump that nylon to my heart's content with no worries.   It all is meaningless until I get outside on real turf.

 

I hear all day, every day from bloggers how "accurate" all monitors are, but I never see the proof.   Forget about spin and launch angles for a minute.  Here's a simple MGS test I'd like to see. You get your GC2, Trackman, Flightscopes and you hit balls into a real fairway with a guy standing downrange who can spot the actual carry locations and roll out locations of real shots hit off grass and you measure them.  Then you compare these measured numbers to what the monitors say.  

 

Why do I never see this kind of test?   I just hear guys state, "Oh they're accurate" based on their perceived "feel" that the numbers are right.   Then we all go on to share our numerous stories about the times when the numbers didn't feel right, or we thought the cheap store sims were jacked, or the shot didn't get read correctly.

[Mr_Theoo 3,360]

I wonder if you'd see different numbers on different mats or are they all the same?

[silver & black 6,420]

Like Mark, I'm a digger with irons. I hit off a mat for a whole Winter one year. When it was time to play for real, I made wheelbarrow worthy divots...lol. It took several outings before I stopped that and started hitting the ball correctly. Well...... more correctly.

[Kenny B 33,460]

I am not surprised with the launch angle and spin rate differences. What surprised me was the difference in grouping between grass and mat. I would've expected the groupings to be similar, but not better for grass. Can someone explain that one to me?

[revkev 25,442]

I've long disliked monitor sessions indoors off of mats.   I think they are garbage, but this may just be that I am twitchy and can't adjust to the conditions.   My wood swing is always off, I'm always afraid of hitting something in the backswing.  They often show me with big sweeping hooks that I don't hit in real life.  Plus I'm a digger with my irons, so a mat always saves every swing and I can thump that nylon to my heart's content with no worries.   It all is meaningless until I get outside on real turf.

 

I hear all day, every day from bloggers how "accurate" all monitors are, but I never see the proof.   Forget about spin and launch angles for a minute.  Here's a simple MGS test I'd like to see. You get your GC2, Trackman, Flightscopes and you hit balls into a real fairway with a guy standing downrange who can spot the actual carry locations and roll out locations of real shots hit off grass and you measure them.  Then you compare these measured numbers to what the monitors say.  

 

Why do I never see this kind of test?   I just hear guys state, "Oh they're accurate" based on their perceived "feel" that the numbers are right.   Then we all go on to share our numerous stories about the times when the numbers didn't feel right, or we thought the cheap store sims were jacked, or the shot didn't get read correctly.

I think you are mixing your metaphors here Mark. I'm certain that a launch monitor outside with a qualified operator is extremely accurate, as accurate or more so perhaps than the guy marking it off method. The issue is how accurate it might be if One is hitting off of a mat inside. That's the uncertainty issue or perhaps the certain it's not so accurate isse that's at stake.

[MmmmmmBuddy 1,570]

I'm not a low spin guy.  I can't tell you exactly what they were, but they were quite a bit higher than my cousin, launch angle was also higher.  When I was getting fit for my current irons on the TrackMan it was giving me long distances with spin and launch angles that were "perfect" for the irons I was hitting.  I will get more data my next go around.

 

goes to my point. If you are a higher spin player IRL, sometimes the monitor will miss spin numbers low but never miss ball speeds or launch angles.

 

For example.... If you typically hit your 7 iron with approx 7000 rpm of spin (sort of the industry standard "good number") and it goes 180, when you cut the spin to 3000 but the ball speeds and launch angle stay the same, the distance will go to 215.  Per the Flightscope trajectory optimizer  The higher the speed player is in the box, the more noticeable the difference when the monitor is wrong..  

 

What I suggest taking away is that if you are getting data that looks very out of the ordinary, it probably is a computer issue..  Look at the spin rate first.

[markb 244]

I think you are mixing your metaphors here Mark. I'm certain that a launch monitor outside with a qualified operator is extremely accurate, as accurate or more so perhaps than the guy marking it off method. The issue is how accurate it might be if One is hitting off of a mat inside. That's the uncertainty issue or perhaps the certain it's not so accurate isse that's at stake.

 

Whoa Rev, did you actually just say that a computer simulation of distance is more accurate than an actual surveyed distance?   Assuming that the surveying method is using an calibrated professional laser instrument, its measurements will be accurate down to mere inches.   Even cheap laser rangefinders are accurate to 1/2 a yard.   Maybe I'm unique, but I'm not really interested in theoretical yardages computed in a TRON world of idealized temperature, pressure, humidity and elevation.   I want to see how far a ball actually goes and how close the gizmo estimator can get to that real world number.

 

No matter what which launch monitor is used, they ALL have at least one computational estimate -- that of roll out -- because even Trackman and FS can't follow the ball on the ground.   That's why they usually tell us to ignore roll out.  Roll out may be unimportant for irons, but it's extremely important for drivers and it's a function of spin, ball speed, and angle of descent.  Athough Doppler systems measure the actual flight of the ball to get carry distance, they can't know the condition of the turf.  They can't spot individual bad bounces or feel the friction of the grass.   Photometric systems have to guess all this and more based on a few inches of ball movement.

 

When you say that you're "certain" that a launch monitor in the hands of a qualified operator is "extremely accurate", how certain are you?   Of course, each manufacturer's marketing department assures us they are accurate, and no golf company has ever been known to make inflated or unsubstantiated claims, right?   Has any of us actually had a monitor session staked out and the shots verified the way they do on Big Break?   No, we haven't.   So we don't really "know"; we just assume.  Granted, in many cases we have a pretty good feel based on how we've hit that club in the past and how that conforms to the numbers we're given, but we don't know.

 

I'd really like to know.   If I were a rich man (or had a golf blog), I think I'd like to take a TM, FS, GC2 and others to that long-drive grid in Mesquite and hit balls onto it and then stake out where they actually went compared to where the gizmos said they went.   Then I'll actually know which is the most trustworthy and which is the least.

[Mr_Theoo 3,360]

Whoa Rev, did you actually just say that a computer simulation of distance is more accurate than an actual surveyed distance?   Assuming that the surveying method is using an calibrated professional laser instrument, its measurements will be accurate down to mere inches.   Even cheap laser rangefinders are accurate to 1/2 a yard.   Maybe I'm unique, but I'm not really interested in theoretical yardages computed in a TRON world of idealized temperature, pressure, humidity and elevation.   I want to see how far a ball actually goes and how close the gizmo estimator can get to that real world number.

 

No matter what which launch monitor is used, they ALL have at least one computational estimate -- that of roll out -- because even Trackman and FS can't follow the ball on the ground.   That's why they usually tell us to ignore roll out.  Roll out may be unimportant for irons, but it's extremely important for drivers and it's a function of spin, ball speed, and angle of descent.  Athough Doppler systems measure the actual flight of the ball to get carry distance, they can't know the condition of the turf.  They can't spot individual bad bounces or feel the friction of the grass.   Photometric systems have to guess all this and more based on a few inches of ball movement.

 

When you say that you're "certain" that a launch monitor in the hands of a qualified operator is "extremely accurate", how certain are you?   Of course, each manufacturer's marketing department assures us they are accurate, and no golf company has ever been known to make inflated or unsubstantiated claims, right?   Has any of us actually had a monitor session staked out and the shots verified the way they do on Big Break?   No, we haven't.   So we don't really "know"; we just assume.  Granted, in many cases we have a pretty good feel based on how we've hit that club in the past and how that conforms to the numbers we're given, but we don't know.

 

I'd really like to know.   If I were a rich man (or had a golf blog), I think I'd like to take a TM, FS, GC2 and others to that long-drive grid in Mesquite and hit balls onto it and then stake out where they actually went compared to where the gizmos said they went.   Then I'll actually know which is the most trustworthy and which is the least.

 

If they weren't accurate why would the pros use them? They're the ones that need to be extremely accurate with there distances more than we do and they trust the data they get from them.

 

Launch monitors may calculate some things like roll out but not factoring things like a bad bounce or something id expect them to be fairly accurate because things like friction of the grass can be calculated.

[GolfSpy Tim 55]

I've seen crazy numbers from the monitor being set for a high elevation

[wbealsd 1,063]

I've seen crazy numbers from the monitor being set for a high elevation

Since my only choice during winter is to hit off a mat, or not at all, I hit off a mat with a GC2.  I always leave my range settings for normal elevation and conditions and find my distances are pretty accurate.  I'm more of a "picker" than a digger, so that might have some bearing on my results, as well.

 

When I play during the week and the course is pretty open, I'm often able to measure my actual distances, so I'm comfortable with the results I get from the GC2.

[Tony Covey MGS 707]

Whoa Rev, did you actually just say that a computer simulation of distance is more accurate than an actual surveyed distance?   Assuming that the surveying method is using an calibrated professional laser instrument, its measurements will be accurate down to mere inches.   Even cheap laser rangefinders are accurate to 1/2 a yard.   Maybe I'm unique, but I'm not really interested in theoretical yardages computed in a TRON world of idealized temperature, pressure, humidity and elevation.   I want to see how far a ball actually goes and how close the gizmo estimator can get to that real world number.

 

No matter what which launch monitor is used, they ALL have at least one computational estimate -- that of roll out -- because even Trackman and FS can't follow the ball on the ground.   That's why they usually tell us to ignore roll out.  Roll out may be unimportant for irons, but it's extremely important for drivers and it's a function of spin, ball speed, and angle of descent.  Athough Doppler systems measure the actual flight of the ball to get carry distance, they can't know the condition of the turf.  They can't spot individual bad bounces or feel the friction of the grass.   Photometric systems have to guess all this and more based on a few inches of ball movement.

 

When you say that you're "certain" that a launch monitor in the hands of a qualified operator is "extremely accurate", how certain are you?   Of course, each manufacturer's marketing department assures us they are accurate, and no golf company has ever been known to make inflated or unsubstantiated claims, right?   Has any of us actually had a monitor session staked out and the shots verified the way they do on Big Break?   No, we haven't.   So we don't really "know"; we just assume.  Granted, in many cases we have a pretty good feel based on how we've hit that club in the past and how that conforms to the numbers we're given, but we don't know.

 

I'd really like to know.   If I were a rich man (or had a golf blog), I think I'd like to take a TM, FS, GC2 and others to that long-drive grid in Mesquite and hit balls onto it and then stake out where they actually went compared to where the gizmos said they went.   Then I'll actually know which is the most trustworthy and which is the least.

 

The accuracy of the carry numbers isn't really in question. The OEMs have all done the testing, and I've actually asked this exact question to a few different R&D guys. At one time or another, nearly every OEM has verified the accuracy of launch data using high speed camera systems to validate what the launch monitor is reporting.

 

Worth a mention, the disclaimer is in everyone's product literature. It's usually something along the lines of accurate to within 2 yards at 300 yards...or some such.

 

Initial launch is pretty basic...technically it's not unlike rocket science actually, but the point is, if you can accurately capture ball speed, launch angle (both vertical and horizontal), spin rate, and axis tilt, you can relatively easily (for math guys) calculate everything that happens until the ball lands. So it's wildly inaccurate to say photometric systems guess. They simply do the math.

 

I will say that we are aware of certain systems that don't always get the math right, and can provide an unrealistic distance advantage for specific launch conditions, but the systems being discussed here are consistent, and do the math right. The ripple here is that each unit has a separate default baseline...essentially a starting point for environmental variables like temperature, humidity, and altitude. In some cases you can tweak those to reflect where you are...or where you will be. For example, Trackman's feature set allowed me to see how the G30 I was hitting in Phoenix, AZ would perform for me in New York. This accounts for very slight variances in numbers across different monitors, but consistency is key. Almost without exception, the club that produces better results under one set of conditions will produce better results under different conditions (higher humidity, higher temps, for example).

 

As you correctly stated, you're left to the algorithms of each manufacturer's roll out model to determine total distance, and they all have separate settings for ground conditions (fast/dry, normal, wet/slow). People may not be comfortable with using math in this way, but the reality is there's no such thing as consistent roll out. Ground conditions are changing all the time, so I'd argue it's actually more beneficial to leverage a consistent model rather than rely on the conditions of the day...especially when you're concerned about apples to apples. Once again, each LM manufacturer's rollout model is a bit different (similar, but not 100%), so you will see some variance from FlightScope to Trackman to GC2, but again, consistency is the thing.

[whiskey golf 61]

I'm late to this thread but that's pretty crazy to see how different the shots off the mat are from shots off grass. 

[Kenny B 33,460]

I am not surprised with the launch angle and spin rate differences. What surprised me was the difference in grouping between grass and mat. I would've expected the groupings to be similar, but not better for grass. Can someone explain that one to me?

I still don't know why the grouping for grass was better than the grouping for the mat. Seems like there are more variables off grass, so what am I missing here?

[Mr_Theoo 3,360]

I still don't know why the grouping for grass was better than the grouping for the mat. Seems like there are more variables off grass, so what am I missing here?

My guess would be it's harder to hit down on a mat as opposed to grass. Not so much that the mat can't be hit down on as much as grass but the mental aspect. I know for me I sometimes struggle to hit down as much cause im scared of hurting my wrist again