VisTrak Installation VisTrak Eagle VisTrak SCX VisTrak EV VisTrak KX VisTrak LX Video Swing Capture Videos

 

Ball Spin Setup

Selecting the Ball Spin Detection method

There are currently 4 methods of ball spin detection:

1.

Spin calculated using balls without markings

The spin rate is then calculated from ball and club data.

Note that as long as the shot is reasonably straight,

the difference between measured and calculated ball spin is mostly marginal

2.

Using balls with spin dots on them

The spin rate is then measured

The advantage of using spin dot balls compared to using the ball logo or line,

is that you don't have to bend down to align the ball logo or line to the camera.

3.

Using balls with a line or strong black logo

This method is mostly very accurate but requires the user to bend down to align the ball logo or line to the camera.

4.

Random or no markings on ball

i.e. using balls without any special markings.

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VisTrak SCX Ball Spin Detection

Random, Talor made Pix or no markings on ball method

Detecting spin from Taylor Made Pix balls

Current test results show that spin detection works best with the Taylor Made Pix balls

Main reasons are that

1. In contrast to using the ball logo, no matter what ball in flight frames are used to calculate the spin, there are always 2 frames showing the Pix images

2. In contrast to launch monitor proprietary balls with spin dots on them, TaylorMade Pix balls are readily available in any golf store for a regular ball price

Measuring Ball Spin from an overhead ceiling mounted camera

using image pixel shift and rotation matching methods

This method consists of taking an array of pixel levels of the ball image in 2 adjacent frames

and obtaining a match with a series of pixel shifting and rotation procedures.

Using this method, rotation (and thus back and side spin) can be detected even with just a smudge mark on the ball.

i.e. this method is not looking for any specific dots or markings on the ball

so any ball can be used as long as there's something on the ball that is not pure white.

Using balls with spin dots on them

The biggest issue users are having is that the spin dot itself is not being detected due to incorrect ball Line/Spot GS (Gray scale) setup.

The above image (from a customer shot video) shows the issue with longer exposure times

and out of focus lenses when attempting to detect ball spin dot markings.

Exposure times need to be under 200 us to reduce motion blur caused by the ball traveling at high speeds.

Nether-the-less, if increasing the Ball Spot GS (gray scale) to 200,

then even out of focus and blurry ball dots can be detected.

Note that only well defined and spaced spin dot balls or balls with a strong logo can be used ( as shown above).

Note that camera exposure time (i.e. shutter speed) has to be set at or below 100 micro seconds and frame set to 1500 fps.

Lighting requirements in order to measure ball spin with the ceiling mounted SCX

Measured ball spin requires clear non-blurry images of the ball in flight so that ball markings can be clearly seen.

This can only be accomplished by reducing the camera's exposure time to below 200 micro-seconds,

which in turn requires strong lighting.

If not using the narrow beam IR lights (as featured in the SCX IR),

the system will have to feature additional lighting.

i.e. 4 LED track lights

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When using the CM Vision narrow beam angle lights, camera shutter speeds can be reduced to well under 100 micro seconds.

This will ensure that ball motion blur is at a minimum and ball markings are clearly visible

GSA Golf Hi-intensity CM Vision IR narrow beam lights

Track Lighting

4 hi-power LED zoom-able track light system with 800 Lumens per light with track

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Note that the VisTrak systems require that the camera shutter speed has to be at or below 200 micro seconds

if ball spin is to be measured and not calculated.

Note that the "Ball line/Spot GS" (Gray Scale) may ( depending on your lighting )

have to be adjusted up or down in order to detect the ball spin dot or ball logo.

System automatically selects the best 2 frames of the ball in flight to measure ball spin

You can also re-calculate the spin with other frames of the ball in flight just by selecting the frame and clicking in the spin video box.

Ball Spin detection using the ball logo

for overhead SCX and Eagle systems

You can now select the option "Spin line / Logo on ball" to measure ball spin for overhead camera systems (i.e. SCX and Eagle).

As the logo will not always be visible in the frames, the system now automatically scans for 2 adjacent fames showing the ball logo

in all the 16 ball speed frames.

Side Spin

Note: When the system is unable to determine side spin from marked balls,

then side spin is calculated from the relative club face angle to path and not just from the face angle itself.

Examples:

1.Draw

If club path is 10 degrees in-to-out and face angle is 5 degrees open, then relative club face angle is -5 degrees closed

which results in a negative side spin and the ball will curve back left after starting off right (i.e. a draw)

2. Pull draw

If club path is 10 degrees in-to-out and face angle is -5 degrees closed, then relative club face angle is -15 degrees closed

which results in a negative side spin and the ball will curve left after starting off left (i.e. a pull-draw)

3. Push

If club path is 5 degrees in-to-out and face angle is 5 degrees open, then relative club face angle is zero degrees

which results in a zero side spin and the ball shot is a straight push right

3. Fade

If club path is 0 degrees and face angle is 5 degrees open, then relative club face angle is +5 degrees

which results in a positive side spin and the ball shot is a curve to the right after starting out straight

3. Push Fade

If club path is 10 degrees in-to-out and face angle is 15 degrees open, then relative club face angle is +5 degrees

which results in a positive side spin and the ball shot is a curve to the right after starting out right

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VisTrak EVi / LX2

Ball Spin Detection from the Side camera

Note that no additional lighting is required with the LX2 and EVi (near) systems as the light source is very close to the ball

The default camera exposure time for the LX2 Vcam is just 50 micro seconds

New spin detection method for side mounted camera systems (i.e. EV and LX)

The method consists of rotating ball spin frame 1 in single degree steps and comparing it to the ball spin image 2.

A best match test is performed which returns the amount of rotation between the two frames.

Knowing the amount of rotation and the time taken, accurate ball spin can be calculated.

Note that any ball markings can be used.

Using the ball logo or line

When the EVi or LX Vcam is placed close to the ball (i.e within 12 to 16 inches),

the camera detects ball spin rate using either the ball logo or ball spin dots.

The difference between the 2 angles ( known as the Delta angle ) represents the amount of ball spin rotation in degrees between 2 frames.

Together with the frame rate time, the spin rate can be calculated based on the amount of rotation using the below formula.

RPM = ( degrees of rotation / 360 degrees) / time in minutes.

Using just the ball logo

Using balls with spin dots on them

The Vcam with EVi and LX systems view the ball from the side.

Rotation - when using spin dot balls - is calculated around the center of the ball between frames

Note that the "Ball line/Spot GS" (Gray Scale) may have to be adjusted up or down in order to detect the spin dot or ball logo/line.

EV Ball Spin Detection from the overhead camera

Ball spin can also be measured from the EV overhead camera

Rotation and spin axis is calculated by comparing x and y spin dot deviation positions between frames

Ball spin for Putts

Measured ball spin when putting is done without the requirement to use ball markings.

 

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Spin Dot / Ball Logo Detection issues

In order to detect the spin dots on the ball or ball logos, the images should be sharp and clear.

In order to achieve this, the camera exposure time has to be fast (i.e. around 100 us) with bright lighting.

If the exposure time is too long (i.e. 300 us plus) then image blur will occur and the dots will appear faint.

Adjusting the "Ball Line/Spot GS" (gray scale) to a very high level (i.e. 200) can help though.

Click above to read more about ball spin detectionn theory...