SkyTrak Driver Carry Distance (Again)

[AnthonyZ]

SkyTrak – Driver Distance
I understand from reading numerous threads on this forum that a number of us have found that SkyTrak measures Driver (and for some iron) carry distances significantly shorter than measured under real life course conditions or as measured by launch monitors such as Trackman and Foresight - GCQuad or GC2. That has been my experience as well. (A number of people also claim that SkyTrak is accurate if set-up correctly).

During the winter months I practiced and took lessons at an indoor range that has a TrackMan and a GC2 and I could consistently generate a driver ball speed of 132 to 141 mph (club head speed of 90 to 96 mph) and carry distances ranging between 220 to 240 yards. I also tested my SkyPro and found that it fairly accurately measures club head speed. We all know that ball speed trumps club head speed for generating carry distance.

I am pretty convinced that my SkyTrak set at my locale 500-feet of elevation is under calculating driver ball speed by approximately 8 mph which translates to a loss of approximately 15 to 20-yards of carry distance for my driver swing attributes. (With my 7-iron, I am seeing 130-yards of carry distance whereas I should be seeing 140-145 yards of carry on well struck shots with a club head speed of 75-78 mph on Trackman and GC2). SkyTrak set at an elevation of 5,000-feet tends to generate more realistic driver carry distances (albeit flight height, side spin and descent angle should be lower if the SkyTrak algorithm simulates the effect of thinner air accurately).

I decided to run a few tests in outdoor conditions and made sure that my SkyTrak was/had:

• Reset - SkyTrak little hole on the bottom;
• Mat and SkyTrak are dead level;
• Lined-up to target;
• SkyTrak level with base of the mat;
• Clean lens;
• Laser pointed at the base of the tee or slightly forward;
• Black Tees;
• No reflective background; and
• No direct exposure to sunlight.

Baseline – SkyTrak vs. TrajectoWare 1.0
I ran a baseline sample of 12 of my better drives (on a bit of a lethargic early Friday evening) on SkyTrak and compared it to the results that TrajectoWare 1.0 generated and found the carry distance on average to be within 2-yards. In both SkyTrak and TrajectoWare 1.0, I used the Greater Toronto Area elevation of approximately 500-feet, temperature 80 degrees F, and 0 mph wind conditions. I used Bridgestone e6 Soft and TaylorMade Project (a) balls. (TrajectoWare 1.0 is freeware developed by Dave Tutleman and Frank Schmidberger that unfortunately doesn’t appear to be available any longer). I input the SkyTrak – ball speed, launch angle, back and side spin data into TrajectoWare 1.0. SkyTrak calculated an average ball speed of 129 mph and 213 yards of carry distance relative to 215 yards carry distance calculated by TrajectoWare 1.0 or a small difference of 2-yards. (I know that SkyTrak club head speed is at best an approximation but I was surprised that TrajectoWare 1.0 generated the same average 87 mph).

During this session, I used my SkyPro which measured an average club-head speed of 90 mph (club-head speed ranged between 89 to 94 mph). Plugging in an average club head speed of 90 mph and from the table below, the average SkyTrak launch angle of 19.3 degrees, spin of 2530 rpm, side spin of -122 rpm into TrajectoWare 1.0 generated a ball speed of 134 mph and 230 yards of carry distance or an increase of 17-yards relative to what SkyTrak measured.

SkyTrak - 500 Feet Elevation, 80 F, 0 mph Wind									TrajectoWare Drive 1.0 - 500 Feet Elevation, 80 F, 0 mph Wind
SHOT	BALL	LAUNCH	BACK	SIDE	SIDE	OFFLINE	CARRY	CLUB	CLUB	CLUB MPH	CARRY	CARRY
# DRIVER	MPH	DEG	RPM	RPM	DEG	YD	YD	MPH	MPH	DIFF.	YD	YD DIFF.
1	125	17.8	2120	-152	-5.6	-31	208	84	84	0	205	-3
2	127	21.4	2477	106	3.3	19	214	86	86	0	218	4
3	127	23.1	2921	293	1.6	18	208	87	86	-1	216	8
4	128	19.3	2725	-432	4.8	4	212	87	87	0	216	4
5	129	21.9	3109	312	4.6	32	211	89	88	-1	219	8
6	131	20.8	2855	122	3.4	21	219	89	89	0	225	6
7	127	16	2724	273	-3.9	-6	205	87	86	-1	208	3
8	127	19.7	2002	-715	0	-34	213	86	86	0	208	-5
9	131	19.9	2019	-786	-3.6	-55	219	88	88	0	219	0
10	131	15.8	2340	-440	-3.7	-36	215	89	88	-1	214	-1
11	131	17.4	2929	294	-1.8	4	215	89	89	0	221	6
12	129	18.3	2140	-339	-3.7	-33	218	87	87	0	216	-2
AVG	129	19.3	2530	-122	-0.4	-8	213	87	87	0	215	2
Median	129	19.5	2601	-23	-0.9	-1	214	87	87	0	216	3
Min'm	125	15.8	2002	-786	-5.6	-55	205	84	84	-1	205	-5
Max'm	131	23.1	3109	312	4.8	32	219	89	89	0	225	8

Calibration – SkyTrak Elevation to Approximate Realistic Carry Distance
According to Titliest (https://www.titleist.com/teamtitleis...l-aerodynamics), the percentage distance increase (relative to sea level) for drives can be calculated by multiplying the elevation (in feet) by 0.00116. For example, the SkyTrak average drive (table above) that carried 213 yards at 500 feet elevation should see an increase of 12 yards at an elevation increase of 4,500 feet (4,500 x 0.00116 = 5.22%) for a total carry distance of approximately 225 yards.

The table below illustrates that a 4,500 foot in increase in SkyTrak elevation yields driver carry distances that should be expected at an elevation of 500-foot setting. (TrajectoWare 1.0 checked). Setting SkyTrak at an elevation of 5,000 feet (increase of 4,500 feet) yielded an average gain in carry distance of 14-yards to 19-yards or a carry distance of 227-yards which is more inline with a club head speed of 90-91 mph as measured by SkyPro (and a smash factor of 1.45+).

I iteratively solved for ball speed using TrajectoWare 1.0 (set at an elevation of 500-feet). I input the SkyTrak measured launch angle, back and side spin and adjusted the ball speed in TrajectoWare 1.0 till it matched the 5,000 elevation carry distance measured by SkyTrak. On average, TrajectoWare 1.0 estimates that SkyTrak under estimated ball speed by 8 mph at 500-foot elevation. The table also reports that TrajectoWare 1.0 calculated a club head speed of 91 mph which is in line with an average carry distance of 227-yards and the approximate 90-mph club head speed measured by SkyPro.

SkyTrak - 5000' Elevation, 80 F, 0 mph Wind								TrajectoWare Drive 1.0-500' Elevation, 80 F, 0 mph Wind
SHOT	BALL	LAUNCH	BACK	SIDE	SIDE	OFFLINE	CARRY	BALL	CLUB	BALL MPH
# DRIVER	MPH	DEG	RPM	RPM	DEG	YD	YD	MPH	MPH	DIFF.
1	121	20	2125	61	0	3	220	131	88	10
2	130	16.9	2326	-506	-1.9	-29	232	139	94	9
3	125	19.4	2013	-202	-5.9	-36	228	134	90	9
4	125	16.2	2515	252	-3.7	-7	216	132	89	7
5	126	22	2039	-599	1.7	-22	227	134	90	8
6	124	22.3	2284	-295	1.7	-6	223	132	90	8
7	125	21.8	2209	95	-1.7	-3	225	133	89	8
8	131	18.2	2544	-403	-1.7	-26	233	138	93	7
9	127	20.3	2886	165	1.6	13	223	134	91	7
10	130	17.7	2332	-268	-3.6	-29	232	138	93	8
11	127	19.6	2058	326	-5.3	-8	229	136	91	9
12	130	20.1	2647	227	-5.3	-15	230	136	92	6
AVG	127	19.5	2332	-96	-2.0	-14	227	135	91	8
Median	127	19.8	2305	-70.5	-1.8	-11.5	228	134	90	8
Min'm	121	16.2	2013	-599	-5.9	-36	216	131	88	6
Max'm	131	22.3	2886	326	1.7	13	233	139	94	10

I appreciate the above wasn’t an easy read or of particular interest to many, but I would be interested in hearing if you are experiencing similar ball speed and carry distance discrepancies.

[3on3putt]

So is the trajectoware assuming a 1.50 smash factor when calculating its numbers? What about the type of ball that trajectoware is using for its calculations?

Also, both gave you a club head speed of 87 (and you even said you were surprised that even the trajectoware gave you 87). So for the first model (500 feet) you used 87 as the club head speed and the carry distances were very identical.

But then for the second model (the 5,000 feet) you used an average of 91 mph club head speed to calculate your trajectoware numbers. That extra 4 mph of club head speed is good for 9 yards of carry distance.

So if I'm interpreting this right, you registered 87 on the skytrak but then just "gave" trajectoware an extra 4 mph of speed and then compared the distance to skytrak at 87mph(?) Of course it's going to be longer. Why not use 87 for the 5,000-foot model as well? You're basically taking the numbers that skytrak gave you, adding 4 mph to the club head speed and recalculating the numbers to show a longer carry distance.

[Morini]

You clearly like data as much as I do, but I got a bit lost in all the detail. I am not exactly what you are trying to do. If you are concerned about ball speed, no point muddling the ball data with ball flight model.

Elevation has no impact on ball speed.

I am not totally following why you are going into such detail on comparing the skytrak ball flight model to Trajectoware, including elevation calculations etc. Are you attempting to find find the elevation that compensates for missing ball speed, or something else?

Also, while I have used trajectoware in the past, I am not convinced it is proven accurate. I would use flightscope trajectory optimizer to verify if needed.
.

[DS12]

I plugged some numbers into Flightscope optimizer from the tables and it does look like Skytrak has under represented the carry distance in both instances. I used shot #2 from the 5000 ft elevation and got 233 carry at 500ft and 245 carry at 5000 ft.

[3on3putt]

Could you screenshot it? I wasn't getting anywhere near that (but have never used the flightscope optimizer before so probably just user error on my part). That's a neat tool.

[DS12]

Maybe I had user error. After reading about needing to total the back and side spin readings, I am much closer to Skytrak numbers on the Flightscope trajectory optimizer

[Morini]

I am still confused about what you are trying to do. The skytrak ball flight model is solid. It has one issue and that is lack of spin decay.

I think you have your Skytrak set to side spin rather than spin axis, correct? I think that is why you have discrepancy in ball flight model.

[AnthonyZ]

Gents, thank you for your replies, questions and suggestions!

@Morini – you got it – I am trying to figure out the elevation that compensates for my strong hunch that my SkyTrak is under estimating ball speed and carry distance. I totally missed the setting for side spin vs. spin axis and not sure what the difference is (apologies for my ignorance). I believe my SkyTrak was set to side spin. Is the spin decay issue that SkyTrak doesn't accurately measure how spin is reduced over the duration of ball flight - for example -500 rpm of impact side spin should produce a nice draw but SkyTrak over estimates the resultant offline carry?

In a nutshell I was trying to quantify how much SkyTrak is off in ball speed and ultimately carry distance. I thought that if SkyTrak and TrajectoWare yield similar results under identical elevation and climactic conditions (which the first table illustrated), then short of buying a TrackMan or GC2 (which isn’t going to happen), how much would I need to tweak SkyTrak’s elevation setting to approximate carry distances representative of my swing.

The second table was generated by new swing data but with SkyTrak set at 5000 feet of elevation which forced/fudged a higher carry distance similar to what I believe I experience on courses or with higher end launch monitors. As a check I thought, if TrajectoWare yields almost identical results at the same elevation, that by plugging in the 5000 foot elevation carry distance into TrajectoWare set at 500 foot elevation I could verify the height adjustment ball speed/club head speed that would translate into.

@DS12 I wasn’t aware of Flightscope Optimizer before and just tried it. I am a little confused as to what inputs are needed relative to SkyTrak for Launch Angle (H) ___ deg and L or R ___ deg.

[Burtgolf]

Based off the large difference in your launch angle and spin rates I would guess your hitting it all over the face of your clubs. Ball Speed is always going to be different with just a slightly off center strike as well as spin.

I know your talking about your SkyTrak readings but to me I would think you would want to know your strike. Get a can of powdered foot spray and spray the face of your driver/irons so you can check you impact location. I think once you get your impact more center strike your ball speeds will be more consistent along with spin and launch which will then let you know if it really is your SkyTrak not measuring correctly or not.

If I am wrong and your data is from your center strike shots then yeah something doesn't smell right.. try the foot spray on the SkyTrak

[Burtgolf]

AnthonyZ Most people are not aware of where they are making contact with the ball which is the most important thing in your golf swing. There are tons of drills and tips out there to help you though if your not able to get to a pro to take some lessons. Even the tips on this site are really helpful I would highly recommend browsing through some of them https://golfsimulatorforum.com/forum...uction-academy

Good luck and hope you get the results your looking for!

[Morini]

Anthony, if you have it set to side spin you have to combine side spin and backspin to get total spin

[3on3putt]

So it took 50 shots to come up with 12 that you could use?

[Morini]

Ok, I sort of get it now.

Here is one important thing to understand. You probably already know this intuitively or even formally, but just need to understand the terms in context:
There are two ways of reporting spin:

• Spin and the axis (tilt) it spins on.
• Spin split into two vectors: side and back (vertical).

My advice is that from now on stick to spin axis. When you have it set to side spin, the "back spin" is only the vertical component, so when you punch it into trajectory optimizer you are missing spin.

Skypro is quite accurate on club head speed, so you are indeed missing about 8 mph. Why not figure that out instead of trying to compensate? As you already mention, altitude reduces impact of spin, so flatter and less curvature.

First of all, all the setup tweaks in the world are unlikely to change your ball speed readings. In general the setup tweaks will lead to fewer no-reads, but ball speed is pretty well what it is. It is possible that dirty glass, dirty ball etc could interefere a teeny bit with finding centroid of ball in images, but they will not lead to consistently losing 8 mph. Also small chance that you have a reflective club head that gets picked up, but it would not be that consistent.

There are two possibilities:

• The ball really is travelling 8 mph slower than you think
• Skytrak is miscalibrated

Anything is possible, but the latter is highly unlikely, so the easiest thing would be if you could hit side by side with Trackman. Even a Mevo would do.

First of all, your drives launch VERY high. Second they spin quite a bit. If you have footspray, spray it. Your smash COULD be consistently low. Unlikely, I know, but so is miscalibrated Skytrak.

If you do hit side by side with Trackman and it reads low, do send it in for recalibration.

Finally, with regards to Trajectory Optimizer,:
Launch Angle (H) is side angle (positive or negative)
Spin Axis L or R is spin axis, L for negative R for positive.

[Morini]

On second thought, spin is probably reasonable, maybe a teeny bit high. Launch angle is definitely high though. LPGA at 140 mph ball speed launches it 13 degrees. That is with hitting 3 degrees up. As per your own table, you average 19.3 degrees. LPGA average that with 7 iron.

[3on3putt]

This is all comes back to the question of how does elevation affect ball speed? And the answer is that it doesn't. You said your goal was to identify the elevation at which your skytrak begins to underestimate ball speed and carry distance. And while elevation certainly has an effect on carry distance, it has absolutely nothing to do with ball speed. So essentially you're saying that the skytrak ball speeds should be higher because you were hitting at a higher elevation. But that is simply not true. Ball speed is ball speed no matter the elevation.

You manipulated the ball speeds and entered whatever ball speed the trajectoware was showing based on the 5000 foot carry distances from the skytrak. But those ball speeds wouldnt change no matter what elevation you are hitting at. You need to re-run the data using the same ball speeds that the skytrak was giving you because this is your true ball speed at that (or any) elevation.

[3on3putt]

Yeah I think you're right in that's what he was going for. Bottom line is that Skytrak has been compared head to head against Trackman in laboratory testing and has performed to within 2% of Trackman (which is basically the gold standard). So to make a claim that the Skytrak is 15-20 yards short is a pretty tough sell IMO.

Anthony --- how long have you had the Skytrak (or how old is the unit?) It's pretty well-known that the laser curtains don't last forever and they eventually need to be replaced. Is this "short" distance a relatively new thing? How long have you been hitting on the Skytrak and feeling like the yardages were short?

Also, although Skytrak can certainly be used outside, I would think that your best chance of getting the most accurate readings would be indoors.

[Morini]

I don't know the loft of your driver, but if we switch the topic from ball flight physics to impact physics, how is it possible to launch 20 degrees with driver loft 12 degrees or less? This is not a criticism, just trying to understand the physics. You can hit 8 degrees up, but that is nearly impossible. More likely adding dynamic loft in some way, creating oblique angle which of course reduces club head speed. I'd say focus on figuring out where the extra 5+ degrees of launch angle come from. That is your mystery to solve at this point in time. Skypro may help with this, as it does report a somewhat accurate angle of attack.

[Burtgolf]

Morini - I am one with a 9 degree driver and try to launch it at 17 - 20 degrees with 1700-2000 backspin .. this is what I found to be optimum carry distances for my ball speeds using the flightscope launch optimizer. I am around 4 to 5 degrees up on path with driver if that helps.

Morini commented
Yesterday, 02:45 PM
I don't know the loft of your driver, but if we switch the topic from ball flight physics to impact physics, how is it possible to launch 20 degrees with driver loft 12 degrees or less?

[3on3putt]

Also, your 500-foot carry distance in the skytrak averaged 213 yards and your 5,000-foot carry distance on the skytrak averaged 227 yards.

You said that "the percentage distance increase (relative to sea level) for drives can be calculated by multiplying the elevation (in feet) by 0.00116. For example, the SkyTrak average drive (table above) that carried 213 yards at 500 feet elevation should see an increase of 12 yards at an elevation increase of 4,500 feet (4,500 x 0.00116 = 5.22%) for a total carry distance of approximately 225 yards."

So in other words, your carry distance was expected to increase by 12 yards with the elevation change and it increased by 14 yards (despite a slightly lower ball speed). So if anything, the skytrak was being overly generous. You were "supposed to" carry it 225 and you carried it 227. Seems pretty accurate to me.

So if the titleist math you used said it should go up 12 yards and it went up 14 yards, what exactly is the issue here?

[AnthonyZ]

The issue is that I strongly believe that I have to tweak the elevation setting to some level be it 5000 ft or otherwise to approximate carry distances experienced on the courses that I play or on TrackMan and GC2.

[3on3putt]

Yeah, I see what you're getting at now. See my comments/questions from the post above.

[wbond]

Why do you believe your skytrak is wrong? Have you taken it outside to verify? Have you taken it to the other place where you use trackman or the GC2? I don't think you have, but maybe i missed it in your thread if you have done this. If not, you have not confirmed that there is an issue with it. All it could show is that you swing differently at different locations.

[Morini]

Like I stated ealier in a comment, figure out where the extra 5+ degrees launch angle come from. If you add dynamic loft, it will absolutely take away ball speed due to oblique angle. That is just physics.

[AnthonyZ]

Gentlemen, thank you again and I do appreciate your suggestions and for challenging results shared! (I did my best on the write-up and appreciate it was a bit to wade through).

The weather here in Toronto is very unseasonably cold for mid-May (and now unseasonably rainy) and hopefully I will manage to get out and give this another go. I have had my SkyTrak for a year and have only really used it in the past couple of months given that golf courses are closed due to the COVID-19 lock down. (This device and my backyard set-up has been a sanity saver when the weather co-operates). My sense from all of your comments is that from your experience SkyTrak is fairly accurate at calculating ball speed and carry distance. (I am still not convinced).

Question:

1. What is the optimum launch angle and back spin for a Driver Club Head speed of 90-95 mph? Here is what I gleaned from the web (ball speed would be handy but I am guessing the table below assumes a smash factor approaching 1.5).

Attack angle https://golfweek.usatoday.com/2016/0...ining-yardage/

This chart shows how attack angle affects launch angle, spin and distance, based on TrackMan data. It’s a common refrain that a high launch with low spin creates optimal launch and distance; this chart shows that correlation.

Clubhead Speed	Attack Angle (Degrees)	Launch Angle (Degrees)	Spin Rate (RPM)	Carry Distance (Yards)
90	-3	12.7	3,064	202
90	-2	13.2	2,970	204
90	-1	13.8	2,878	207
90	0	14.3	2,786	209
90	1	14.8	2,696	211
90	2	15.3	2,607	213
90	3	15.9	2,518	215

For now, here is what I can not do for now:

• Hit a driving range or golf course (fingers crossed courses open soon in Ontario)
• Compare my results to TrackMan/GC2 as indoor ranges are not an essential service and likely to be closed for the foreseeable future and the indoor range that was open pre-COVID-19 doesn't facilitate recording and sending shot history).

Here is what I will try:

• Record one set of drives with elevation set at 500' (which approximates the Greater Toronto Area courses I play)
• SkyTrak settings - "Spin Axis"
• Put impact tape on the face of my driver (my strikes tend to be middle of face - and the occasional high toe strike which generates a high launch draw/hook)
• Record club head speed with my SkyPro (I believe I can integrate it with SkyTrak if I use an IOS device like an iPad and will try that)

[DS12]

Ping optimal launch/spin chart with ball speed and angle of attack

https://mobile.twitter.com/pingtour/status/1189599768823005184

[AnthonyZ]

DS12 - I like the PING chart as it provides combinations of optimal back spin with launch angle to generate carry distances, e.g. 130 mph ball speed/19.2 degree launch/2000 rpm spin = 225 yards of carry. That tells me for my avg launch angle of about 19 degrees - I am generating 300-600 rpm of excess spin.

[Morini]

Careful with that chart. There is a reason why LPGA launches 13. Those numbers are computer generated, and I wish they didn't exists. How exactly does somebody get 19 degree launch with 2000 spin without losing ball speed? Hit up 10 degrees with 9 degree driver? The tee would need to be illegally high.

[Morini]

LPGA all the way as your reported CHS is right at LPGA average. See below. I know that Tutelman had an article about getting the absolute maximum distance out of a given clubhead speed. I hope you didn't read that and got carried away.

If you hit the middle of the face, how can launch angle be that high? You must be adding a ton of dynamic loft at impact. I wouldn't overthink things right now, and try to hit "up" etc. This idea has ruined so many recreational golfers. Just get a clean hit on the ball with a reasonable launch window. If you remove the dynamic loft and hit center face two things will happen. Your launch angle will go down significantly and your ball speed will jump instantly to high 130's if you are indeed swinging around 93-94 MPH.

Just be mindful that unlike footspray, impact tape does affect spin significantly. You may want to video face on to see what is happening. Finally, hitting outdoors is one thing that can affect ball speed in my opinion. It depends on the amount of direct light (should be none), but I also suspect that a lot of ambient light reduces contrast with ball. If you want to make sure, try it in evening.

[LEO MODE]

Sorry didn't read everything, only your initial post but I suggest you use a different flight model than Trajectoware. It's an older program which doesn't have a full capability and a few algorithm is a bit off. I suggest you use OptimalFlight instead as it's the closest you can get to Trackman outdoor data.

Secondly, I verified this already but Skytrak carry algorithm model is extremely good. The hardware itself doesn't have the full capability of reading correct ball speed over 150mph, but the software algorithm model based off of ball data is very solid.

Lastly, I don't think SkyPro can be a good comparison device to measure or even estimate your other relative data. My advice to you is at least try to compare with (if you can get hands on them) OptimalFlight, Trackman or Flightscope outdoor data.

Please let me know if you need more help.

[LEO MODE]

As I said it doesn't mean what you think it says but if you want to believe it the way you want to believe it's perfectly fine (look at the keyword, max difference). But again, I apologize if you misinterpreted it. I will revise it so people won't misinterpret.

[3on3putt]

Ultimately none of this matters because the original poster's ball speed is nowhere near 150 anyway.

[LEO MODE]

I posted because he was referring to carry distance vs ball flight algorithm model that is outdated, and a club head measurement which should take it with a grain of salt. All in all, both were not an industry standard to measure to properly conclude if Skytrak was off or not in the first place. I only mentioned ball speed, not because of OP's concern but just to highlight a different flaw that is not related to the carry data the OP questioned. I did note that I didn't read any other posts other than OP's initial one though.