Xi+ first impression

[Clubfitter73]

Thanks Clubfitter. So what do you think the minimal distances are for radar units? Would it be different for Trackman vs Flightscope?

I think you should always follow the manufacturers advice. There are things we don't know about the units making it impossible to guess what the limit is. If one of the units uses a slower cpu to read and interpret the radiowaves bouncing of the ball then that in itself will already force the user into using more distance for that unit. If one of the units is using software (firmware) that is less optimized to do the calculations then again that has its consequences. Until a user reversed engineered his unit we simple don't know

[Clubfitter73]

On the other hand if you have my swingspeed (95 mph) spinn has very little impact on overall distance.

But huge influence on Angle of descent

[Clubfitter73]

Optimal Flight or Trajectoware are nice softwares. I used optimal flight which is very affordable and get frequent updates.
I just swapped to trajectoware which is free but get no updates but its really easy to use. I will stick with Trajectoware due to the ease when simulating path alterations.

The trajectoware data is checked with OptimalFlight before they released it. As trajectoware is not updated and they are not making it open source and it's only correct in the 1000-4000rpm bandwidth I personally think Optimalflight is the better software to use.

[Maverick]

Good discussion here. Thanks for joining the forum clubfitter73.

[Bubba22]

Great input clubfitter.

[FaultyClubs]

When the spin on that same ball is 5000 rpm (rotations per minute) or 83.3 rotations per second that 0.074 will allow the ball to rotate 6.2 times. at 290cm 4.5 rotations. As the metal dot can only be measured while facing the radar that 6.2 can easily become 5 rotations measured and that 4.5 easily only 3 rotations measured.

A Doppler radar doesn't work that way. The spinning dot cause a frequency shift around the doppler centroid (ball velocity), this frequency shift is then measured to determine spin rate. The resolution of the frequency shift is determined by the effective doppler bandwidth and the accuracy by the signal to noise. There are many ways to implement this but none actually "count" the number of revolutions of the ball! The problem indoors is signal to noise (limited signal and lots of clutter) hence the metal dot. The metal dot is included to improve the signal to noise (not to be counted). But even so I doubt indoor spin measurements would be as accurate as outdoor.

[Dax]

A Doppler radar doesn't work that way. The spinning dot cause a frequency shift around the doppler centroid (ball velocity), this frequency shift is then measured to determine spin rate. The resolution of the frequency shift is determined by the effective doppler bandwidth and the accuracy by the signal to noise. There are many ways to implement this but none actually "count" the number of revolutions of the ball! The problem indoors is signal to noise (limited signal and lots of clutter) hence the metal dot. The metal dot is included to improve the signal to noise (not to be counted). But even so I doubt indoor spin measurements would be as accurate as outdoor.

I agree with a lot of this, but wonder then why TM would say, "In order to receive measured spin rates, a Special metallic sticker Must be placed on the golf ball." Not sure why they would say this if it were not helping them in some way measure spin.

[Clubfitter73]

A Doppler radar doesn't work that way. The spinning dot cause a frequency shift around the doppler centroid (ball velocity), this frequency shift is then measured to determine spin rate. The resolution of the frequency shift is determined by the effective doppler bandwidth and the accuracy by the signal to noise. There are many ways to implement this but none actually "count" the number of revolutions of the ball! The problem indoors is signal to noise (limited signal and lots of clutter) hence the metal dot. The metal dot is included to improve the signal to noise (not to be counted). But even so I doubt indoor spin measurements would be as accurate as outdoor.

Yes, the metal dot is needed to improve signal to noise level. But that has nothing to do with what I wrote

If the metal dots is not visible (present) in the radar beam then the radar was little change to pick up the signal in a short flight. So if the speed and spin are such that the dot is never visible (present) there is no spin data. That is what I wrote.

I only did the rotations per flight calculations to show to the readers how short that time of flight is and that even a high a spin as 5000rpm during that short time of flight almost no rotation is left for the radar to measure.

If the DSP is good enough then maybe during the half a rotation the metal data is visible for the radar there might be enough data points present to calculate the spin, then that single (or technically a 1/2 ) rotation would be enough however the error margin on that spin value will be rather high. Also during the initial part of the flight the impact generates so much noise that a part of that signal is lost. For TM the absolute minimum is 2 rotations.

PS Imho long range indoor (metal dot) data is much better then outdoor (non metal dot) data.

PSS I tested <$5 radar panels and using the count method (as the ADC resolution was not good enough) it was possible to get within 10rpm of the TM data IF the number of rotations was sufficient.

[Bubba22]

Clubfitter, what parameters are the metal dot mainly required for? Is it spin, launch angle, side angle? The reason I ask is the smaller units like the ES14 etc require no melt dot but ar obviously limited in what they measure.

[fhann]

But the launch monitor, such as Trackman, desires more than 1 sample, i.e. minimally it needs to see/detect the dot twice. The sample size may need to be more than 2 depending upon software/firmware coupled with equipment sensitivity/accuracy along with signal to noise ratio, etc. Flightscope is very similar.

Clubfitter73 has also reminded us that detection occurs within a cone for both the ball and clubhead detection analyses.

[Clubfitter73]

Clubfitter, what parameters are the metal dot mainly required for? Is it spin, launch angle, side angle? The reason I ask is the smaller units like the ES14 etc require no melt dot but ar obviously limited in what they measure.

I don't know but if I would take an educated guess I would say it's needed indoor to measure spin and spin-axis tilt data and also used to improve launch angles and speed measurements data.

[Bubba22]

So even outdoors the metal dot improves the ball data?

[fhann]

The metal dot will not improve measurements outdoors because the TM or Flightscope launch monitor keeps measuring ball data downrange. That dot will artificially affect spin, drag and flight characteristics down range, i.e. similar to how mud on a ball or a knick in the cover will affect the ball flight. Indoors, the ball does not have time to be substantially affected/slowed by additional drag. The ball behaves more like a ballistic object during the first 20 to 30 feet before spin starts to influence lift.

[Clubfitter73]

So even outdoors the metal dot improves the ball data?

They could use the stronger signal the metal dot is giving. No idea if they would, the TM uses the flight length to determine if you are using the unit indoor or outdoor so maybe they also use that to switch calculations routines. No idea what the FS is doing.

But in general metal dot will, like indoor, make the ball signal to stand out more. Might however be that over the longer flight that metal dot, even if it is very light and thin, skew the down range aerodynamic ball behavior

Maybe hitting several balls with and without metal dot and then compare data would give an indication. It's possible to get the full carry length data set from the TM so maybe there is an indication there in that data set to be found, never tried that.... yet .....

[FaultyClubs]

I agree with a lot of this, but wonder then why TM would say, "In order to receive measured spin rates, a Special metallic sticker Must be placed on the golf ball." Not sure why they would say this if it were not helping them in some way measure spin.

Strictly speaking the radar doesn't need a sticker, the ball itself generates enough signal return to produce the frequency sidebands needed to measure spin but indoors the time bandwidth product is so low the signal isn't strong enough to be reliably differentiated from noise so they add a radar reflector (ie metallic sticker) to enhance the signal.

Given doppler frequency sidebands are weak relative to the total radar return, the sticker would be critical for measuring spin rate but not so much for the other stuff.