SkyTrak Launch Monitor

[Maverick]

http://www.skytrakgolf.com/

iPad app:

https://itunes.apple.com/us/app/com.sporttrak.skytrak/id876548058?mt=8

[fhann]

Flightscope optimizer is based upon a driver and its loft and headweight. My trajectory software is by Wishon and is designed to be modeling not only the driver but the irons. Modelling an iron with the output data that you have collected cannot be accurately done using the Flightscope driver optimizing software. I also have a Flightscope launch monitor and am familiar with the driver optimizer software and have confimed with Flightscope technicians that their driver optimizer software is for dirvers, with lofts from 6 degrees to no more than 16 degrees.

Optimal Flight trajectory modelling software is another good option for a software program to model ball flight from irons, hybrids and also woods.

[pctekbr]

bkorwin - Very interesting exercise. Using data from my 6 or 7 and 4 iron the results were very similar (within a yard and a half), using data from a wedge shot Ball speed 67, launch 26.1, horiz launch -5.5, spin 8558, side spin (735 on ST 749 or 4 deg in FS optimizer......) gave carry of 79.5 FS and 66 on ST. 80 sounds about right for what I was trying to do. Did similar with I thin a 9 iron and came up 13 yards short on ST. IF I take the flightscope flight model as a given and I have been on a flightscope enough to be comfortable with it, then I can conclude that the good news is that is appears that ST is capturing the data accurately and its the flight model that needs tweaking. I will run some more shots through both at some point to see what I can tell and see if I can find some sort of correlation. Intersting note is that 13 seemed like the difference when the horizontal LA was to the left and 9 when it was to the right, with 1 or 2 outliers. Its a real pain that my app is not labeling the clubs I am using. as it makes this hard to go back and do. Wondering what would happen if I hit a wedge set to 7 iron? Is the flight model the same for that club and for a wedge? Also wondering if I could see some sort of relationship between variables and difference if I plotted enough items out. I still think that ST is super useful knowing that the yardage under is somewhat constant.

club selection is only for you to monitor your progress in history. it does not change calculations.

[fhann]

Please model the data using Optimal Flight software before jumping to a conclusion based on the Flightscope dirver optimizer software. I never use Flightsope driver optimizer software when anaylzing irons, even though I have the Flightscope launch monitor now for nearly 4 years. COR values are much higher for drivers, spin values much lower for drivers, headweight much lower for drivers versus comparing to a sand wedge.

Can't compare apples to oranges using the incorrect software application.

[pctekbr]

Please model the data using Optimal Flight software before jumping to a conclusion based on the Flightscope dirver optimizer software. I never use Flightsope driver optimizer software when anaylzing irons, even thought I have the Flightscope launch monitor now for nearly 4 years.

frank, can you get us a copy of that software or link? i value your opinion because it seems you know more than we do.

did you run through the output and see any deviations from what ST posted and your software? i know you did #15, how about the rest?

thanks for the help. just trying to understand why we are getting these values.

[fhann]

Here is a url for Optimal Flight software that one can download for a 7 day trial period. http://www.qualitygolfstats.com/

I did not model the others because I wanted to model the straightest shot which should have the highest smash factor. less side spin, and this would assume that the strike was nearly maximized for distance based on a higher level of energy transfer from the club face to the ball.

[bkcorwin]

Great information frank. It was definitely not clear from the website that it was intended only for drivers.

Brian

[fhann]

Optimal Flight output based on data from shot #20. 109.9yards carry distance -2.4 yards offline, (left)

[davray666]

I can confirm the SkyTrak's LA is spot on. LA is actually one of the easiest parameters to measure. This was verified using ProTee's Vertical camera and compared with the GC2. Now having said that, the user must make sure the SkyTrak is completely level. I would suggest using a small carpenter's level. If the unit is not level by 2 degrees, the LA readings will be off by 2 degrees, which will of course affect carry.

For a camera based LM viewing the ball from the side like this one does, it should be. Since I don't have one and therefore have not checked how they do this exactly I have to speculate. The challange is that in order to measure spin you can't have to much time between the images taken by the camera or cameras. If you do your reference will spin out of view. At the same time since they don't know up front how fast the ball will move. They have to safe guard for 200mph+ meaning that time between images is probably in the range of 1ms or less. The accuracy of the algorithm, the resolution of the sensor and a few other things will determine with what accuracy they can measure the ball position. For the sake of argument let's say it's +/- 1mm in the camera plane. If the ball traveled 30mm between the 2 images for a soft shot. The accuracy will be appr. +/- 2 degrees and that is assuming the ball path is aligned with the camera plane and it is not. So it's worse. For a driver shot that traveled say 80mm the accuracy would be appr. +/- 0.3 degrees.
All of this assumes a perfectly aligned and leveled sensor. Since they have an accelerometer I assume they use it. In that case it does not matter how much you level the unit. The accelerometer value will be used. To determine any angle or speed you need to measure the ball position in 3D space. For that you use 2 of the tilt angles from the accelerometer. How the reference value error translates to vertical and horizontal launch angles errors depends entirelly on where in the field of view the ball was captured. It's not as simple as 2 degrees tilted sensor produces 2 degrees of error.
For a better understanding of accelerometer absolute accuracy please read this article written by the guys who make them.

http://www.analog.com/library/analogdialogue/archives/43-05/accelerometer.html

So what does all of this mean. Unfortunatelly it means it can be spot on or not. What is even worse is that it can change from time to time and especially when used in under varying conditions such as temperature and light.
GC2 is by the way designed to operate just like that. Don't know much about the ProTee vertical cam but I assume it's one of those systems that takes pictures with a huge FOV and typically captures the ball when it has traveled more than 1 meter. If properly leveled and aligned those tend to be accurate provided they find the ball.
There are multiple ways to solve all of the mentioned problems and that's why I am looking forward to get my hands on a unit so I can see how well they did it.

[bkcorwin]

I would be curious what the optimal flight model shows in terms of changes to carry distance and max height for a wedge shot based on the magnitude of changes that are possible in launch angle caused by sensor capabilities. The flightscope driver model shows relatively small changes in carry distance based on 2 degrees of variability in vertical launch angle.

So, is the accuracy in launch angle a large enough effect such that leveling is a dramatic influence on accuracy? I would also be curious to hear if EVERYONE is having issues with wedge distances. Franks flight model indicates that skytrak may not be far off. I wonder if there are other factors in how people are estimating their on course carry distances? Slope? wind? Biases in our ability to internally average our resulting distances to come up with our mean yardage for a club?

[Maverick]

Since they have an accelerometer I assume they use it. In that case it does not matter how much you level the unit. The accelerometer value will be used. To determine any angle or speed you need to measure the ball position in 3D space. For that you use 2 of the tilt angles from the accelerometer. How the reference value error translates to vertical and horizontal launch angles errors depends entirelly on where in the field of view the ball was captured. It's not as simple as 2 degrees tilted sensor produces 2 degrees of error.

The GC2 is a different animal. It's possible the accelerometer in the Skytrak is not as sophisticated or not use in the same way as in the GC2. In my case, tilting it 2 degrees will change the LA bias by 2 degrees.

[Mike Z]

Frank, Thanks for your insights. I agree that a flight model built for a driver would not necessarily yield very reliable results for other clubs depending on the way the underlying calculations are done and the what specific variables measured versus calculated. Yet, the FS link provided earlier produces results that are much more in-line with expectations, something you could look at and say, yeah, that makes sense versus something that you look at and say no way to. Which is another way of saying that I'm pretty sure that there is an issue. The data I gathered from the provided link seemed to corroborate what I thought so I deemed it reliable. May well be coincidence. The conclusion jumped-to in this case is that I'm more correct than the software about the way I hit the ball in question. That's the thing I cannot reconcile in my mind. I am not trying to argue, but I am trying to understand so please help me understand where my logic is flawed: Head weight and COR along with head speed would have everything to do with ball speed but is largely irrelevant when actual ball speed is what is being measured and input. Spin will also affect but the ball does not care what club produced it. At a given launch angle, spin and speed the ball should behave under the laws of physics the same exact way no matter what club hit it. What am I missing?

[davray666]

The GC2 is a different animal. It's possible the accelerometer in the Skytrak is not as sophisticated or not use in the same way as in the GC2. In my case, tilting it 2 degrees will change the LA bias by 2 degrees.

That is actually good news. It means the sensor can be properly aligned and leveled and that the shot data is not contaminated by bogus accelerometer readings. What we need now is a reference surface. E.g. is the bottom of the unit properly aligned in the factory so we can use a leveled surface that we place it on.
Next question related to accuracy to Skytrak (and Foresight sport) in case they read this would be "what ball speed is assumed for the quoted launch angle accuracy".
If we get that it's easy to calculate how it will deteriorate/improve when ball speed goes up or down.

[fhann]

Frank, Thanks for your insights. I agree that a flight model built for a driver would not necessarily yield very reliable results for other clubs depending on the way the underlying calculations are done and the what specific variables measured versus calculated. Yet, the FS link provided earlier produces results that are much more in-line with expectations, something you could look at and say, yeah, that makes sense versus something that you look at and say no way to. Which is another way of saying that I'm pretty sure that there is an issue. The data I gathered from the provided link seemed to corroborate what I thought so I deemed it reliable. May well be coincidence. The conclusion jumped-to in this case is that I'm more correct than the software about the way I hit the ball in question. That's the thing I cannot reconcile in my mind. I am not trying to argue, but I am trying to understand so please help me understand where my logic is flawed: Head weight and COR along with head speed would have everything to do with ball speed but is largely irrelevant when actual ball speed is what is being measured and input. Spin will also affect but the ball does not care what club produced it. At a given launch angle, spin and speed the ball should behave.

You are not missing anything when you have accurately measured data for ball spin, ball speed, launch angles both vertical and horizontal and finally the spin axis. With this data, provided the ball modelling software has the correct alogarithms for ball flight, then it does not matter what club is used to hit the ball. What does matter is the software program's ball flight algorithms to properly model the ball flight. The algorithm for ball flight for a driver is different than for an iron.

I must apologize about the remark I made about the Flightscope software. On my Flightscope launch monitor software, the software is designed for dirvers only. The Flightscope ball flight optimizing software on their website is good for irons and woods.

I modeled shot #20 on the Flightscope web page and get 111 yards carry and ball lands on the left side of center line. It matches pretty well with both SkyTrak and Optimal Flight software results.

I hope that I do not offend too many people here, but nearly 98 percent of my clients that have shown up for fittings have vastly overestimated their average carry distance for nearly all of their clubs. Most of my clients have stated carry distances for their irons that have matched up to their maximum total distance. I have the luxury of using my launch monitor to provide real time data collection of carry distance for my shots using my game ball under outdoor conditions. Temperature, wind, elevation and ball type can both positively and negatively affect the measurements in real time conditions.

[pctekbr]

Frank, Thanks for your insights. I agree that a flight model built for a driver would not necessarily yield very reliable results for other clubs depending on the way the underlying calculations are done and the what specific variables measured versus calculated. Yet, the FS link provided earlier produces results that are much more in-line with expectations, something you could look at and say, yeah, that makes sense versus something that you look at and say no way to. Which is another way of saying that I'm pretty sure that there is an issue. The data I gathered from the provided link seemed to corroborate what I thought so I deemed it reliable. May well be coincidence. The conclusion jumped-to in this case is that I'm more correct than the software about the way I hit the ball in question. That's the thing I cannot reconcile in my mind. I am not trying to argue, but I am trying to understand so please help me understand where my logic is flawed: Head weight and COR along with head speed would have everything to do with ball speed but is largely irrelevant when actual ball speed is what is being measured and input. Spin will also affect but the ball does not care what club produced it. At a given launch angle, spin and speed the ball should behave.

You are not missing anything when you have accurately measured data for ball spin, ball speed, launch angles both vertical and horizontal and finally the spin axis. With this data, provided the ball modelling software has the correct alogarithms for ball flight, then it does not matter what club is used to hit the ball. What does matter is the software program's ball flight algorithms to properly model the ball flight. The algorithm for ball flight for a driver is different than for an iron.

I must apologize about the remark I made about the Flightscope software. On my Flightscope launch monitor software, the software is designed for dirvers only. The Flightscope ball flight optimizing software on their website is good for irons and woods.

I modeled shot #20 on the Flightscope web page and get 111 yards carry and ball lands on the left side of center line. It matches pretty well with both SkyTrak and Optimal Flight software results.

I hope that I do not offend too many people here, but nearly 98 percent of my clients that have shown up for fittings have vastly overestimated their average carry distance for nearly all of their clubs. Most of my clients have stated carry distances for their irons that have matched up to their maximum total distance. I have the luxury of using my launch monitor to provide real time data collection of carry distance for my shots using my game ball under outdoor conditions. Temperature, wind, elevation and ball type can both positively and negatively affect the measurements in real time conditions.

hey frank,
on the flightscope optimizer, what numbers are you using for launch angle (h) and altitude?

when i put in just the ball speed (94), launch angle (v) (30.7), ball spin (8098) and and spin axis (left 1.6) i get 121 carry and 126 total. just trying to see where you are getting 111 yards.

[Mike Z]

First off, no offense at all. I am trying to figure things out, that's all and I appreciate your insight. For the record, I put the data from my shot on post 840 into optimal flight and got 75.2 carry. That is between FS and ST but a whole lot closer to FS (66, 75, 80). And its also well within the range I can say makes sense. I know within a range how far a well-struck golf ball will go. I also know the miss. These aren't based on the once in a lifetime "I can hit it THIS far" but are based on hitting it squarely. Everybody nukes one sometimes - that;s not my number. I still don't understand why the algorithm is different for a driver versus an iron, unless the calculations are super complex and in order to simplify would reply on a set of assumptions that work within a relevant range. With computers, seems like that would not be necessary. I guess I will just have to accept that I may never understand that part and get back to figuring out how to achieve my golf goals: I have worked very hard over the last few years to make the percentage of well-struck go up.. It has. Now its time to hone in on the scoring clubs. I want more than to know that an 80% gap wedge will be about 90 yards if I hit it right and that an 80% sand wedge will go about 80. I want to get to the point of having an 85 yard shot, an 80 at 75, etc. as well as working on direction control with feedback throughout the winter. So figuring out this tool is how I will accomplish that. And I am confident that I will. just a matter of seeing enough info to make sense of it all. Again, thanks for your insights.