Mevo+ data parameters

[kahi]

It would be great to know in detail what the Mevo+ measures directly (and how) and what it calculates using the direct measurements (and how).

Here's the list of the parameters copied directly from the Flightscope FAQ, please help out with filling in the missing information and please no speculation:

Carry Distance CALCULATED (also outdoors, Mevo+ tracks only partial flight)
Club Head Speed CALCULATED (how?)
Smash Factor CALCULATED (ball speed divided by club head speed)
Apex Height CALCULATED (also outdoors due to partial flight tracking?)
Flight Time CALCULATED (due to partial flight tracking)
Ball Speed MEASURED
Vertical Launch Angle MEASURED
Horizontal Launch Angle MEASURED (or is it? how?)
Lateral Landing CALCULATED (due to partial flight tracking)
Angle of Attack CALCULATED (how?)
Total Distance CALCULATED
Roll Distance CALCULATED
Spin Axis MEASURED (how? Flightscope has a patent on getting the spin axis, US20190049571A1 -> does Mevo+ utilize a method from this patent? Or something else?)
Spin Rate MEASURED (how? Flightscope has a patent on a measuring protocol, US9868044B2 -> does Mevo+ utilize this method? Or is this calculated?)
Spin Loft CALCULATED (how?)

Since many parameter values are calculated, the quality of the values depens on not only the measuring quality of Mevo+ but also a lot on the quality of the algorithms used in their flight and club head modelling. So hopefully it's not difficult for Flightscope to finetune the software for e.g. carry distance accuracy.

[pwade3]

Flightscope has stated via webinar that spin axis is measured and not calculated.

https://www.crowdcast.io/e/fs-golf-app-with-mevo

At the 4:45 mark.

[kahi]

Yeah, I saw that also. Do you know how they measure it?

I'll edit my post on that.

[pwade3]

No, above my pay grade. 🧐.

[pwade3]

Do they not have to measure club V & H paths to get AOA?

[kahi]

I don’t know. Let’s hope this topic grabs the attention of someone who does.

I sent a while ago a request to Flightscope to have a webinar on the parameters but got no reply.

[mikestuewe]

Some of the things you mention like smash factor and spin loft are calculated because they are mathematical calculations. Including them here, when every other launch monitor calculates them as well is unnecessary.

[kahi]

I simply listed all parameters that Flightscope lists for Mevo+. Of course we don’t need to discuss e.g. smash factor, no open questions there.

Let’s try to find out the answers to the questions.

[Obedt]

My understanding from their explanation is that indoors at least one receiver is focusing on the dot, and using its revolutions to measure spin & spin axis.

The spin axis issue with misshits on longer clubs though leads me to believe that it requires a certain amount of revolutions or data measurements and without those it will provide an estimate (possibly using club data).

I really like this thread idea. Problem is that FS may not want to divulge too much info on the “how” of their calculations. Hopefully we find out more!

[kahi]

Flightscope and the other high end manufacturers have been pretty open in the professional markets to describe in detail how they measure or calculate and how accurate they think they are. Let's hope they bring that openness to the consumer market, too. I mean it should be normal to describe how a device measures something, right? If I buy a TV or a car, I don't have to guess the technical details, they are listed by the manufacturers and verified by independent testing.

The FS patent "Ball Spin Rate Measurement" has an excellent description on spin measurement with a radar in general in the "Detailed description" section. They describe in detail why e.g. the metallic dot is useful. It magnifies a lens effect that enables spin measurement. It's really interesting reading!

But let's try to find out what method for spin and spin axis measurement they have used in Mevo+. I would assume the same harmonics-based method described in the patent but would be good to get a confirmation on this.

[Bubba22]

Interesting that angle of attack is calculated. So if you select wedge and hit driver what is the angle of attack numbers? I suspect they use club data to calculate spin axis otherwise there should be no gear effect influence on off center hits.

[kahi]

I don't know whether it is calculated in Mevo+ or measured. I hope someone can clarify, I'll change it to measured if it is measured. I would personally hope Mevo+ is measuring club head parameters like path and AoA, that would be great!

But let's hope we get someone who knows to confirm the AoA as well.

[schurlette]

mevo+ most certainly measures club head data and uses it in its algorithms. And I believe that this data is used extensivley in their flight model. The reason why I believe that is quite simple: Occasionally my mevo+ registers a chip/pitch in the 20-40 yard range when I make a practice swing. The actual ball does not move at all, but in the sim the ball travels pretty much the distance of the intended shot. In my understanding that is only possible if the unit uses club head data for the calculations.

After a few months with the mevo+ I have the impression that the unit relies heavily on club data for its flight model.

[kahi]

Interesting! Do you know which club head parameters it measures?

One way of estimating the spin axis is to use club path and ball horizontal angle to try to calculate the axis.

[kahi]

Spin axis, ways of measuring/calculating it, from the Flightscope patent application:


"Current Doppler radars use indirect methods to estimate golf ball spin axis. One example is to estimate the spin axis from analyzing the lateral curvature in the trajectory, and the horizontal trajectory, from which spin values can be estimated . This method is limited in that it has to observe the ball flight for an extended time period (not possible in an indoor test environment or fitting studio), and is affected by wind which disturbs the trajectory, and radar alignment errors.

Another example is to measure the relative directions of the club and the ball at impact, and to calculate an estimate of the horizontal and lateral spin components that can result from the strike.

Current camera-based systems are also used to measure golf ball spin axis. Cameras are generally poor at measuring high speed objects such as moving golf balls. High speed cameras are costly and suffer from difficulties in alignment, illumination, and measurement reliability .Many camera-based spin measuring systems also require some form of ball marking. Current methods also usually involve determining complex three dimensional movement from limited and blurred two-dimensional images, leading to inaccurate results or even failing to provide a result.

This disclosure addresses these problems and provides a system and method to directly measure the ball spin axis from signals received in multiple spaced Doppler radar receivers.

The systems and methods proposed herein use a Doppler radar with an array of appropriately spaced receivers to measure a golf ball spin axis. The Doppler radar typically has a transmitter co-located with multiple receivers (typically three or four). The receivers are arranged and spaced in a predefined pattern with at least two forming a horizontal pair and two forming a vertical pair. In a more general case the arrangement can be in any perpendicular set of coordinates. The transmitter and receivers are placed in a vantage position from which the golf ball launch can be measured, for example several feet directly behind the ball tee position.

The signals received immediately after ball launch are analyzed to determine the time differences received in a vertical receiver pair and a horizontal receiver pair. If four receivers are used, two vertical and two horizontal pairs can be arranged to provide two independent measurements in the horizontal and vertical directions, with improved statistical accuracy.

The spin axis is calculated as a trigonometric function of the ratio between measured time horizontal and vertical time differences."

[tonybrown32]

kahi this is a good read, and got me thinking... speculation of course... bu Flightscope continues to say that spin axis is "measured". Could it be they purposefully leave out mentioning if spin axis is directly or indirectly measured? Directly measured meaning, looking at the dot and ball spin axis and relaying that information. Indirectly measuring meaning, using other directly measured parameters (face angle/path) to provide an indirect measurement..

Both = measured parameters, so saying spin axis is "measured" isn't wrong, but may be misleading... Would also support schurlette theory that club head data is heavily used to indirectly measure some items like spin axis, when there are not enough revolutions to directly measure.. I share this theory as well.

Just food for thought the more we discuss..

[kahi]

Good food for thought! Let’s find out how it is. I wish FS would tell us.

[kahi]

https://apps.fcc.gov/oetcf/eas/repor...c_id=QXP-LJ361

Mevo+ has four reception antennas so accurate measurement of angles, spin rate and spin axis is possible! So the FS statement that spin axis is measured and not calculated seems valid (which is great)

[pwade3]

Then I wonder why the crazy right spin axis with toe shots. Heel shots show a left axis which is unusual. Other LM’s that read ball spin are showing opposite including the ST I had. Center hit shots were fine.

[kahi]

If only FS gave us the answer. The four receivers do not guarantee accurate measurements and data analysis, they merely make it possible. But perhaps it’s something that can be fixed in firmware. Let’s hope so.

[keither5150]

pwade3 If the Mevo + is showing crazy fade spin axis with toe shots, whereas the side by side sim is showing the opposite. Perhaps at times the Mevo + uses club data as a backup or accuracy check. If this is the case, they simply have it backwards and this could be easily fixed with a firmware update. I have hit a fair bit on a Trackman 4 indoors....I have found that toe hits and heel hits have the appropriate amount of SA.....Ball flight seemed to be perfect. I have a inside out swing but 2/3 of the time, I hit my woods nearer to the heel. That off center hit negates the draw spin and my ball flight goes relatively straight with the woods. Calculating spin axis from club data can be very accurate on center hits. As you go to longer and longer clubs, the gear effect increases. You will see very little gear effect on a wedge whereas a driver can be quite noticeable. If the mevo + is measuring club path and strike location... they can easily calculate an accurate SA, when the measured SA doesn't make sense. That data check or back up verification would be a great thing to combat any misreads.

[kahi]

Updated list:

Carry Distance CALCULATED (also outdoors, Mevo+ tracks only partial flight)
Club Head Speed MEASURED (not fully confirmed but evidently so)
Smash Factor CALCULATED (ball speed divided by club head speed)
Apex Height CALCULATED (also outdoors due to partial flight tracking?)
Flight Time CALCULATED (due to partial flight tracking)
Ball Speed MEASURED
Vertical Launch Angle MEASURED
Horizontal Launch Angle MEASURED (confirmed by Henri Jonhson in a video interview with Gung-Ho Golf)
Lateral Landing CALCULATED (due to partial flight tracking)
Angle of Attack MEASURED (not fully confirmed but evidently so)
Total Distance CALCULATED
Roll Distance CALCULATED
Spin Axis MEASURED (confirmed by Henri Jonhson in a video interview with Gung-Ho Golf, Flightscope patent US20190049571A1)
Spin Rate MEASURED (confirmed by Henri Jonhson in a video interview with Gung-Ho Golf)
Spin Loft MEASURED (not fully confirmed but evidently so)

I'm happy now. Let's hope they can iron out the kinks in the firmware to make Mevo+ operate to it's fullest potential.

[kahi]

One correction to above: Spin Loft CALCULATED since there is no way of measuring it directly. The estimation method advertised by both Trackman and Flightscope is to take the Angle of Attack (MEASURED from the directional path of the center of gravity of the club face) and Dynamic Loft (how is this derived?) and subtrack one from the other.

Actually also the club path and face angle should be taken into account but since the simple substraction above is close to the truth, it seems to be used.

Now the only mystery remaining is how Dynamic Loft is measured or calculated? Trackman has stated "calculated from a collision model" but what does that mean exactly?

"TrackMan measures the 3 dimensional direction and speed of the clubhead at impact, in addition the 3 dimensional ball launch direction, speed and spinrate are measured by TrackMan. By measuring these parameters and applying the law of physics this provides the orientation of the clubface at the point of impact on the clubface. This orientation of the clubface is 3 dimensional and are reflected in the data parameters “face angle” and “dynamic loft”. Even though that “face angle” and “dynamic loft” are derived numbers from direct measurements and a collision model, numerous robotic test has proven that this is indeed a very accurate calculation of “face angle” and “dynamic loft”."