Trackman.. An engineering perspective

[vkurup]

I am a bit intrigued by Trackman stats. I am assuming trackman or similar ones use radar like doppler effect to judge things. Working out stats like club speed, ball speed, launch angle, distance etc is fairly straight forward. I just cant work out how trackman can work spin angle, land angle etc. Surely the doppler cannot detect dimples to figure out spin angles.

Is there any documentation on HOW a trackman/flightsope etc work?

 

[moogie]

I am a bit intrigued by Trackman stats. Surely the doppler cannot detect dimples to figure out spin angles.

Normally the golf balls have Silver Dots on that Trackman picks up/reads

 

[CMAC]

Normally the golf balls have Silver Dots on that Trackman picks up/reads

the AG balls dont, in fact any trackman I've used has used 'normal' balls

I'm also interested in the ops question, maybe google?

 

[moogie]

the AG balls dont, in fact any trackman I've used has used 'normal' balls

I'm also interested in the ops question, maybe google?

Sorry DV, but AG DONT use Trackman (none in my AG area anyway)
They have a Launch Monitor of some description, BUT its DEFO NOT a Trackman, maybe Flightscope.....??.....or another model, perhaps

Trackman is a Brand of launch Monitor, very expensive piece of technology too
Ive used trackman twice now, 2 different fitters, and both had their balls marked up with Silver dots

 

[CMAC]

Sorry DV, but AG DONT use Trackman (none in my AG area anyway)
They have a Launch Monitor of some description, BUT its DEFO NOT a Trackman, maybe Flightscope.....??.....or another model, perhaps

Trackman is a Brand of launch Monitor, very expensive piece of technology too
Ive used trackman twice now, 2 different fitters, and both had their balls marked up with Silver dots

theres 4 (I think, maybe 3) at AG Clydebank :smirk: thats the one I've used a few times, your right about some of the smaller AG's

 

[JustOne]

I'm pretty sure it's maths. If you know the speed, direction, launch angle, path of the sweetspot etc etc then you can work out the rest.

 

[moogie]

theres 4 at AG Clydebank :smirk: thats the one I've used a few times, your right about some of the smaller AG's

4 Trackman units...........??
Or
4 Launch Monitors.........??

If they have 4 x trackman units then thats a 6 figure sum invested there

 

[vkurup]

Interesting that they have silver dots... My range has used one of the kits, but we were hitting range balls during the fitting process!!! I am not sure what kit (TM, FltScope, Launch Mo etc) we used.

Even if you have 2 silver dots, I cant see how TM can 'see' such tiny spots using a sound-echo or doppler based system. I am tending towards it being calculated figure rather than a detected figure. Unless the silver-dotted balls are specialised micro chipped TM balls that provide data back to the system - though I would be surprised if it was so.

 

[vkurup]

Hola.. I think i might have an answer...

1) Spin and club angle are derived. Spin can be derived from the trajectory, speed etc

2) In case of indoor where flight path is very short, the spin angle is derived from the mettalic (silver) dots. TM claims they can do it if the ball travels about 14 feet.

More details here..
http://forum.ottawagolf.com/showthread.php?64932-Flightscope-Trackman-clubface-spin

(you learn something new everyday... Happy Christmas)

Some additional reading matter..
http://www.trackman.dk/download/newsletter/newsletter7.pdf

http://www.flightscope.com/index.ph...analyzer-flightscope-tracking-technology.html

 

[duncan mackie]

I'm pretty sure it's maths. If you know the speed, direction, launch angle, path of the sweetspot etc etc then you can work out the rest.

yes and no - if it's a motion it's measured; otherwise it's calculated.

so clubface angle (open/closed), for example, is calculated, ball spin is a measured element.

 

[SocketRocket]

Trackman has the Radar unit positioned behind the ball and unlike the indoor systems it tracks the balls flight with it's Doppler Radar.

It must be a clever bit of software that after measuring the height of the balls flight, the time in flight at various points, the movement right/left, it can work out things like spin rate, launch angle, clubface and swing direction, swing speed and smash factor.

The indoor types must use the reference points on the ball to make their extrapolated data.

 

[Phil2511]

The Flightscope doesn't use markings. The Vector launch monitor needs a solid black line on the ball and the ball set to a specific position so that line faces the Vector at address.
Trackman unsure, was hitting Titleist ProV1 balls in their fitting centre, didn't notice any silver dots but didn't look. If as was posted before the dots only necessary for indoor use then that could explain not seeing any.

 

[JustOne]

yes and no - if it's a motion it's measured; otherwise it's calculated.

so clubface angle (open/closed), for example, is calculated, ball spin is a measured element.

I respectfully think you've got it the wrong way round the face angle would be measured along the lines of the direction the ball started, the spin would be calculated not measured, of course I could be wrong as i'm totally guessing however it still remains that some things are measured and from those figures the rest are calculated.... whichever ones they may be (to me) is insignificant... as long as the figures are accurate

 

[vkurup]

Guys... all the answers you need..
http://forum.ottawagolf.com/showthread.php?64932-Flightscope-Trackman-clubface-spin

 

[Andy]

4 Trackman units...........??
Or
4 Launch Monitors.........??

If they have 4 x trackman units then thats a 6 figure sum invested there

4 Trackman's @ AG Clydebank. Originally installed when range was operated by World of Golf.

 

[Nosevi]

Hi all, new to the forum and just registered. I do know a little about this subject and I hope you don't mind if this answer is a little protracted. As well as having a little experience of active array doppler radars (I've tested one for the military a few years back and had to have a knowledge of how they worked and how different moving objects are effected/tracked by a doppler radar and the 'software fixes' employed) I've used several launch monitors, mainly Flightscope. Personally I own a GC2. Having looked at the X2, upcoming Xi and GC2 I went the camera route, I'll explain why later. I posted up an explanation of why I decided to buy a GC2 on a US golf forum, however after an online 'debate' with one of the 'moderators' in which he spouted rubbish and displayed a complete lack of understanding on the subject (other than the fact that he used Flightscope in his business) and I pointed out the pros and cons of both approaches, all of my posts comparing GC2 to a radar system were deleted - interesting definition of 'Forum'.

Anyway, in answer to the OP's question, doppler radars such as Flightscope can read spin but it doesn't really do it by looking at the dimples as such. It does it by monitoring the harmonics of the beams scattered back from the ball. In layman's terms (not for the OP, clearly) a regular radar sends a 'ping', listens to it coming back and from the time delay gets a distance to the target. It then sends another 'ping', again listens of the returned energy, gets another distance and can work out the speed from a difference between the two. A doppler radar however works in a slightly different way. It sends a very precise frequency of energy to the target. When that energy is 'bounced' back it's frequency will have changed depending on the speed of the object it is 'tracking'. If the object is coming towards the radar the frequecy is increased, if it's going away, such as with a golf shot tracked on radar, it is decreased. An example of this effect is when a car comes towards you and the engine note is high but when it passes and goes away the engine note appears to be lower.

This is a far more accurate way of tracking speed but it also allows for another reading on a golf launch monitor. As the ball flies away from the radar, if it is spinning, let's assume backspin, there is a difference in speed between the top of the golf ball and the bottom. With backspin the bottom of the ball is moving away from the radar quicker than the top. When the radar listens to the returned pulse it doesn't get just one frequency of returned energy, the pulse frequency now covers a range which spans from the fastest part of the ball and the slowest. They can use the average to accurately give ball speed and the difference between the two, as they know the diameter of a golf ball, will give them the spin speed.

There is however one minor snag. Due to the dimple pattern which scatters the beam, size of a golf ball, number of elements in the radar array, it's not possible to determin which bit of the golf ball is going faster and which bit is going slower with any accuracy - they therefore can only measure total spin speed, they can't give the direction of that spin and so spin axis (or sidespin component and backspin component if that's how you prefer to see it). Because of this maths and observation of the effects of spin have to take over. When it comes to Flightscope being used outside it looks at the overall flight shape and the motion of the club (albeit the back of it) through impact. Inside it uses a slightly different and less accurate way of determining spin axis by using the club motion (again the back) and the ball launch vector. Outside they say that wind has a very small effect on the calculation, it's clear that the inside model is less accurate as they would use it outside if it wasn't.

In addition there are some other calculations that have to be made, not measured as the radar is looking at the back of a club not the front. It has to derive face angle and dynamic loft from looking at the club trajectory and ball launch while bearing in mind that they have total spin not spin axis. All of that said it's very clever maths and they are very bright chaps. It's probably pretty close.

When looking at the accuracy of different systems most people (including moderators on US golfing forums apparently) fall into a very simple trap. They hit a ball on a range and see which system gives the correct flight. The radar does as it simply tracks the ball so they conclude that a camera system is inaccurate in comparison, buy a radar system and put it in their shop. What they fail to understand is that a radar system is always going to give an accurate ball flight if it can see it - that's not in debate and is pretty obvious. It may or may not give accurate spin numbers. It should be pretty close on total spin but spin axis (so backspin and sidespin), while it may always appear correct if you can see the flight (as this is what it uses to calculate it) may be a little off. In indoor mode radars use different methods to determin spin axis and use that to predict ball flight. They determin total spin in a similar way though although with a shorter flight a metal dot helps.

In a nut shell a radar system will always say where THAT last shot went, it may however get the 'how did it get there' a little off. A camera system such as the GC2 (at least should) give you accurate spin numbers and launch condidtions. Whether your ball goes exactly where it predicts is dependent on whether you're at sea level in a given temperature, pressure, wind, etc. I went the GC2 route because I didn't want to know where the last shot went, I wanted to know how I hit the ball. Both are pretty good systems though, it really depends on what you want them for.

Sorry strayed a tad off topic with the GC2 but does demonstrate the only minor down side in a doppler radar system.

 

[duncan mackie]

I respectfully think you've got it the wrong way round the face angle would be measured along the lines of the direction the ball started, ......

you answer the point yourself if you are deriving the face angle from the ball starting line (I agree with your derivation but it's still derived/calculated.

From Trackman - but I'm not competely convinced this is as definitive as they suggest; especially as the smash factor doesn't have a * !!!


TrackMan data gathered on every shot

Club Speed Ball Speed Height
Attack Angle Launch Angle Carry
Club Path Launch Direction Side
Swing Plane Spin Axis Total*
Swing Direction Spin Rate Side Total*
Dynamic Loft* Smash Factor Hang time
Spin Loft* Landing Angle Last Data
Face Angle*
Face to Path* (* - Calculated Data)

 

[Nosevi]

Smash factor doesn't have a star because although they do calculate it it's merely the ratio of clubhead speed and ball speed, both of which they have very accurately. I posted a complete explanation of how and why a doppler radar system tracks spin as well as it's drawbacks, but the system didn't post it. Just rewritting in word to cut and paste (lesson learned). be back to you in a mo......

 

[Nosevi]

Oh well, the forum just popped in my earlier post. Hope that explains it a bit.

 

[JustOne]

you answer the point yourself if you are deriving the face angle from the ball starting line (I agree with your derivation but it's still derived/calculated.

Yes, you are of course correct Duncan, it's a calculation taken from a measurement :thup: (I even wrote it as such, DOH!)