Clubhead & Ball Speeds Are Correct...but Yardages Are Hugely Inflated...

[Sixmudd]

Looks like this thread has run its course. OP says his set up is fine, he’s done all the leveling, using good balls, logo facing camera etc. OP then just needs to send the unit back to skytrak to see if they see any issues with it. Could be , or could not be. But as Morini suggested, take it with you to your next TM session. And if you’re still it happy after that, then sell it or return it.

[Morini]

Iphysical set up of the unit, .

Having unit at wrong height can lead to really messed up ball data, including spin. But it is obvious with random reads. Unlikely for mid trajectory in any case.

or the lighting,

Too much direct light can interfere and create no-reads and misreads. But there would be fluctuations and randomness. You cannot have too little light, it works in the dark.

or the position of the golf balls,

Balls at extremes of field of view can experience misreads and no reads. But unlikely for mid trajectory, and as above, would not be consistent

internal damage

Unlikely that internal damage would affect only one variable spin. So extremely unlikely.

or some other variable we have not covered

Anything is theoretically possible. Occam's Razor says that you have low spin in your home setup. I'd do the tee test again, and not at a weird angle. I'd also foot spray your club and use center strikes as your good strikes. I'd also align skytrak properly, place a target on the target line and only use shots with minimal side angle.

[Morini]

The tee itself was offset to the right of the net center, so I angled the SkyTrak unit to the left a bit to compensate. Not sure if that had anything to do with the visual representation showing little draws every time, or if they impact the the side spin calculations.

Angled causes you to swing differently. Skytrak doesn't care where you are aiming, it reads side angle relative to unit. Visual representation is based on modeled ball flight. Modeled ball flight is based on ball data. Ball data had spin axis. Spin axis was caused by your swing, not setup.

They were not little draws.

[Morini]

So how do we know if Swing Caddie is any good at REPORTING an item such as "backspin" if it is not actually measuring it...and is instead only predicting it based on the aforementioned algorithms? Becasue in head-to-head tests versus Flightscope and Trackman, Swing Caddie somehow mangaes to consistently come within 1.5-5% of the numbers that these much higher-end machines report. If you trust Trackman and Flightscope, then you can trust Swing Caddie to within a 1.5-5% margin of error...not on every individual shot mind you, but definitely on an averages over a number of shots.

Assumptions are made that fall apart during atypical situations. If you give an algorithm some data such as height, age, occupation and lifestyle it can probably guess your body weight with remarkable accuracy. Just assumptions based on correlations, not actually measuring your weight. Get an atypical person, way off. Just like your spin.

I give up at that his point. Take your Skytrak to your next TM session.

Skytrak is accurate on the vast majority of shots (80%), with about 15% minor and 5% major misreads. It is possible you have a bum unit, but unlikely because a bum unit wouldn't get reads. It is as mentioned really really hard to screw up spin photometrically. You compare rotation between two images with known interval time. It is just physics. The odd time an unclear image slips through and it misidentifies spin. But no chance that it would do it consistently. The camera doesn't lie.

[Rogala]

I was curious about this as well, which is why I asked about the swing caddie side spin (never used one so not at all familiar with them). There's a good amount of side spin on these shots. 7 of the 10 were offline by 12 yards or more .... with a 7-iron. The 3 shots that managed to stay somewhat online all happened to be the 3 shots with the most backspin and had far less side spin. Is the excessive side spin taking away from the backspin count? In other words, shot #3 had just under 4,000 backspin and just under 2,000 sidespin. Should we be interpreting that as more like just under 6,000 total spin? I guess what I'm getting at is if you hit two balls and one is dead straight and the other is a big hook, the hook will probably register as having less backspin, because a large amount of that ball's spin is side spin. So is the excessive curvature of these shots affecting the backspin display?

I am more of a TGC player and less of a Skytrak range rat, so perhaps I'm interpreting Skytrak's display of backspin vs. side spin incorrectly. But that was just my thought upon noticing those side spin numbers.

I found the "offline" numbers today interesting, as each shot I posted hit a 1 foot square target in the dead center of my hitting net (which is about 9 to 10 feet away from the tee off which I was hitting).

The tee itself was offset to the right of the net center, so I angled the SkyTrak unit to the left a bit to compensate. Not sure if that had anything to do with the visual representation showing little draws every time, or if they impact the the side spin calculations.

Yesterday's shots seem to have had very little side spin vs. today's numbers....but, maybe I just learned that I have a tendency to hit little hooky pull-draws off a short tee vs. off a mat ?? I suppose that this knowledge alone, if accurate, would help me on medium length par 3s. A SkyTrak success story on day 3. :-)

That being said, someone else advised me to turn on the "spin axis" feature on the session settings, which I forgot to do before I posted, as this supposedly gives a more accurate representation of total spin (at least per their comments). Attached is the same shot data with that done...and it does bump up the average "total spin" RPMs by about 300 RPMs...meaning that they are still 1,500 to 2,000 RPMs lower than my historical numbers over the past 8 years. See attached file for that raw data.

I am guessing that something is still off in my set-up or the lighting or the ball position, etc. It was NOT just my mat. Something is making the RPMs read low...just want to get to the bottom of it...typical engineer I guess. :-)

[Rogala]

Unless there has been an update I am not aware of, I don't think Swing Caddie measures any type of spin. My understanding is that it just estimates it from trajectory and ball speed.

It is possible that I am wrong about the SC spin, but I don't think so. No way skytrak gets spin wrong by that amount consistently. Thus, disregard the SC and ST spin differential.

Second, all the shots used in the Skytrak were calculated on "back spin" not spin, so it understates total spin significantly. With that amount of spin axis, not sure if we should use these shots to draw meaningful conclusions. If these were the "good" shots, what is going on? And why were they chosen to be good? Smash? Smash is meaningless as it is estimated. Ball speed? If the face was shut, club was delofted, so ball speed artificially high. Carry? Same argument as for ball speed. Accuracy? Not with that much spin axis.

Rogala, I think you are working too hard and analyzing too much, when the answer is simply that your spin is low. I don't know what is causing it. It often is caused by mat, but if there is no change with tee, I don't know. Whatever you need to do to address this has nothing to do directly with Skytrak. I suggested you bring the skytrak to your next TM4 session.

All good points / questions. Here are some responses / answers:

1) On Swing Caddie and other Doppler Radar units (forgive me if this is already clear to everyone here) - You probably already know that if you are standing near the road, and an ambulance zips by you with its siren on, that the tone of the siren changes as it goes by (getting lower in pitch as it gets further away)...same thing with the whistle of a passisg train. That's the Doppler Effect as demonstrated by sound waves created by the siren/whistle, and your ears serving as the "sensors" which detect interference patterns int he waves due to physical position.

That principle is the key to understanding how doppler launch monitoring technology works. As the ball travels away from the launch monitor (which is both sending out microwave signals and receivng signals which bounce back to the unit) it provides measurable clues as to how the golf ball is behaving in flight via the "interference pattern" created by the golf ball travelling through the original waves. All doppler radar units use a series of sensors to analyze the wave interference pattern caused by the moving ball and then make flight predicitons based on the feedback data. The data is recorded by internal sensors in the unit, and fed into an internal algorithm to spit out things like ball speed, launch angles, etc.

The more high end the unit (like Flightscope or Trackman) then the more sensors and higher resolution you get. A second radar unit in the same launch monitor box can be used to collect club head data and determine its speed, face angle, etc. Combining the two data sets open up the full range of club and ball data. That capability (and the ability to take it outside to the range / course) seems to be what made TrackMan the leader in this space for so many years.

Swing Caddie is a very low end doppler radar unit...and unlike Trackman has only a single radar source (which measures the ball only, and not the clubhead). Unlike Tracknan, it only measures a very few parameters. Ball speed and trajectory are two of the ones it can measure but actual backspin in not.

So how do we know if Swing Caddie is any good at REPORTING an item such as "backspin" if it is not actually measuring it...and is instead only predicting it based on the aforementioned algorithms? Becasue in head-to-head tests versus Flightscope and Trackman, Swing Caddie somehow mangaes to consistently come within 1.5-5% of the numbers that these much higher-end machines report. If you trust Trackman and Flightscope, then you can trust Swing Caddie to within a 1.5-5% margin of error...not on every individual shot mind you, but definitely on an averages over a number of shots.

2) My own backspin numbers as cited in this thread were collected over an 8 year period in mutiple fitting sessions (all hitting off mats), and every one of them shows backspin averages for a 34 degree 7-iron (2 degrees strong vs. classical numbers) between 5,800 RPMs and 6,300 RPMs (which, I agree, might be a wee bit low vs. other players of similar handicap).

The fact that my cheap little Swing Caddie unit comes up with numbers in that same range day-in and day-out is very heartening...and inspires confidence in that unit.

Now, maybe those numbers are BS...and maybe the Trackman units and even the other camera-based units which took those measurements over an 8 year period did not really provide accutate backspin data. Maybe the new SkyTrak unit is 100% accurate reporting RPM figures which are about 2,000 revs lower. Well, Inguess that it's theortetically possible that all other systems I tried before sucked, but the "experts" seem to say differently...at least when when it comes to Trackman...and the fact that Swing Caddie gets within 1.5-5% of those numbers is also fairly impressive in the eyes of most reviewers.

Note: In my own experiecne, I would say that Swing Caddie is a few hundred RPMs off, but that it is cCONSISTENTLY off, and mostly in one direction....meaning that it is not 1,000 RPMs off on one solid swing, and then only 200 RPMs off on the next one.

3) You also asked "If these were the "good" shots, what is going on? And why were they chosen to be good?"

I chose them only on feel, sound, and on the resulting shot hitting a 1 foot sqaure target in the dead center of my hitting net (marked by a green square held there by velcro straps)...not on any recorded data from the unit. Any ball which hit the target and felt and sounded solid to me was recorded. It took me 14 shots yesterday to come up with the 10 shots I shared. It took me 16 shots today (when hitting off the low tee) to get 10 "good shots". I was hitting the ball with an easy swing yesterday, but today I really took a rip at these shots as the low tee gave me a bit more confidence. The numbers recorded by SkyTrak happen to validate my own fell, hearing and vision when it came to hitting that target, BTW. Note: You can see that one of the "good shots" from yesterday gave some wonky backspin numbers per SkyTrak, but I left it the mix because it felt and sounded like a pure shot to me, and it also hit the 1 foot square target in the center of my hitting net.

4) Look, SkyTrak should theoretically be far better than a low end doppler radar unit like Swing Caddie at reporting backspin, as it is taking actual measurements based on the spinning ball itself..not making predictions based on secondary measurements. That is one of the reasons I bought one.

I am quickly learning that it is only as good a tool as its set-up (which is fine, and to be expected) and that it is clearly very sensitive to positioning. The experience with the leveling feet as the root cause of a 1,000 to 2,000 RPM difference has taught me that already.

It is currently STILL reading 2,000 RPMs lower than data collected over 8 years worth of previous ball and club fitting sessions however...and also 2,0000 RPMs lower than my cheap (but 1.5-5% accurate vs. Trackman and Flightscope) doppler radar unit on the same exact shots hit off both my mat and off a low tee (as suggested by users on this forum).

That's a fact...and I posted the data to prove it. Furthermore, several other threads mentioning low RPMs also exist in this forum...meaning that other users have experienced the exact same thing I am experiencing.

5) Conclusion: Something really does seem to be amiss here. It does not seem to be my hitting mat as today's test demonstrates. It might be either in my physical set up of the unit, or the lighting, or the position of the golf balls, or (less likely) internal damage or some other variable we have not covered. If it is my set up or the lighting or the ball positioning, or "whatever" then I really do want to correct this so that I can rely on the RPM data being generated and not just "pretend it doesn't exist".

Anyway, I would at least try and get the unit operating as accurately as possible...hope that makes sense.

[Morini]

Yes. Also, not sure if it has been mentioned, but he might be offset, which is a recipe for hook spin. Anyhow, the math is simple, just use the backspin and sidespin like the sides of a triangle. The hypotenuse is the total spin, so it is basically pythagoras C2 = a2 + b2.. The average total spin was probably about 4500, not 4024, but still on the low side. Not sure what is causing it.

[wbond]

You cannot discount the fact that he is now swinging inside his own location and likely that he’s just not swinging the same way that he did at other locations

[Morini]

Yes, and also that the SC spin is a red herring.
One of the "good" 7 iron was 36 yards off-line. We simply can't use shots with that amount of spin axis to draw any type of conclusion. I'd be more interested in figuring out source of spin axis than missing spin. But it could be related.

[3on3putt]

Morini -- That makes total sense. Thank you. So in essence ...

1. His total spin is actually higher than he thinks because he's not taking all the side spin into consideration, which is eating away at his backspin amount.

2. That total spin, while higher than he realizes, is still a bit on the low side for a 7-iron for some odd reason.

[Morini]

Yes, side spin takes away from back spin. There are two ways of reporting spin. Total spin, and the tilt it spins on (spin axis). Or broken into vectors, back and side. Obviously if you have significant spin axis, and break into vectors, back spin will be a lot lower than total spin. Moral of the story, set it to spin axis, and only worry about total spin. This thread is a bit of a mess. As mentioned, ignore SC spin, it is estimated. And only look at total spin. The only thing I can't explain is why his spin is low. Tee should help. I do know it is not the Skytrak. It can screw the odd shot, but not consistently. Zero chance of that. Reading spin photometrically is fairly straight forward. But it is not as low as it seems, as total spin is higher given high side spin.

[3on3putt]

Unless there has been an update I am not aware of, I don't think Swing Caddie measures any type of spin. My understanding is that it just estimates it from trajectory and ball speed.

Rogala, if you are going to do such detailed data analysis, you need to have actual data in the first place. It is possible that I am wrong about the SC spin, but I don't think so. No way skytrak gets spin wrong by that amount consistently. Thus, disregard the SC and ST spin differential.

Second, all the shots used in the Skytrak were calculated on "back spin" not spin, so it understates total spin significantly. With that amount of spin axis, not sure if we should use these shots to draw meaningful conclusions. If these were the "good" shots, what is going on? And why were they chosen to be good? Smash? Smash is meaningless as it is estimated. Ball speed? If the face was shut, club was delofted, so ball speed artificially high. Carry? Same argument as for ball speed. Accuracy? Not with that much spin axis.

Rogala, with all due respect, you are way overthinking this. Your spin is low, fact. I don't know what is causing it. It often is caused by mat, but if there is no change with tee, I don't know. Whatever you need to do to address this has nothing to do directly with Skytrak. I suggested you bring the skytrak to your next TM4 session.

I was curious about this as well, which is why I asked about the swing caddie side spin (never used one so not at all familiar with them). There's a good amount of side spin on these shots. 7 of the 10 were offline by 12 yards or more .... with a 7-iron. The 3 shots that managed to stay somewhat online all happened to be the 3 shots with the most backspin and had far less side spin. Is the excessive side spin taking away from the backspin count? In other words, shot #3 had just under 4,000 backspin and just under 2,000 sidespin. Should we be interpreting that as more like just under 6,000 total spin? I guess what I'm getting at is if you hit two balls and one is dead straight and the other is a big hook, the hook will probably register as having less backspin, because a large amount of that ball's spin is side spin. So is the excessive curvature of these shots affecting the backspin display?

I am more of a TGC player and less of a Skytrak range rat, so perhaps I'm interpreting Skytrak's display of backspin vs. side spin incorrectly. But that was just my thought upon noticing those side spin numbers.

[Morini]

Unless there has been an update I am not aware of, I don't think Swing Caddie measures any type of spin. My understanding is that it just estimates it from trajectory and ball speed.

It is possible that I am wrong about the SC spin, but I don't think so. No way skytrak gets spin wrong by that amount consistently. Thus, disregard the SC and ST spin differential.

Second, all the shots used in the Skytrak were calculated on "back spin" not spin, so it understates total spin significantly. With that amount of spin axis, not sure if we should use these shots to draw meaningful conclusions. If these were the "good" shots, what is going on? And why were they chosen to be good? Smash? Smash is meaningless as it is estimated. Ball speed? If the face was shut, club was delofted, so ball speed artificially high. Carry? Same argument as for ball speed. Accuracy? Not with that much spin axis.

Rogala, I think you are working too hard and analyzing too much, when the answer is simply that your spin is low. I don't know what is causing it. It often is caused by mat, but if there is no change with tee, I don't know. Whatever you need to do to address this has nothing to do directly with Skytrak. I suggested you bring the skytrak to your next TM4 session.

[3on3putt]

Does the swing caddie measure side spin? If so, how do those compare to the skytrak side spins?

[RAH5]

I don’t have anything further to add other than we have the Net Return as well and love it.