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Stereo Parallel camera setup Stereo Converging camera setup Camera calibration Carry adjustments Putting and chipping IBS image processing Technical help

Please note:

Regular stereo systems are now EOL (End of Life)

and are replaced with the new VisTrak system.


Click above image to see the VisTrak systems

! Note: this setup procedure is only for the CX stereo parallel camera configuration !

Click the above button to read about CX converging camera setups.


CX Stereo Calibration

Note that all CX Surround systems are individually pre-calibrated so re-calibrating will not be necessary.

Note: please use Control Panel version or greater for this procedure.

Calibration procedure

Should re-calibration be required then the following calibration procedure should be made:

Calibration setup

In order to calibrate, we need to raise a 20cm white strip mounted on a black card from the floor up to the cameras in 10cm steps.

A metric tape measure is suspended from the center of camera casing and extended to the floor.

The above images show two methods of raising the height of the calibration strip.

i.e. you can either use a camera tripod and lab stand or

attach the white strip card directly to the tape measure and simply slide the strip up or down..

Note that calibration table consists of 12 to 30 row entries at set 10cm distances from 300cm to 0cm.

i.e. 300, 290, 280, 270... to 0 cm

If your camera height is not exactly at a 10cm interval (i.e. 283 cm instead of 280cm or 290cm) then a extra entry adjustment will be required later

The Control Panel is set into calibration mode and the height the unit is mounted from the floor is entered into the system using the f and shift/f keys.

12 Calibration steps

The above image shows the white strip connected to the tape measure with the slider.

Using the calibration slider on the tape measure, a complete calibration can be done in 10 to 15 minutes.

When testing, set both RAW Path and RAW Launch angle to ON

You can view the complete calibration table by selecting the "Show calibration table" option.

Focal Length and Pixel Width (PWX) adjustments

Focal Length and Pixel Width adjustments should be set to values that reduce distance measurement corrections to a minimum.

In the above image ( taken in the office here) show that the distance correction for the calibration strip is 1.57 cm.

i.e. as the measured distance the strip is from the camera is 228.43 cm when its real distance is 230cm,

a 1.57cm correction value is required to correct the 228.43 cm to 230.cm.

CX Surround Accuracy

The above test results table sample shows near perfect path and ball speed accuracy.

Launch Angle - as May 2018 - still requires tweaking a bit but still very good.

We doubt that any of our competitors can beat these figures. Not that anyone could confirm their claims to this degree of accuracy anyway.

Lens focal length

Note that standard H and V cams use lenses with a focal length of 3.5mm so ensure that the 3.5mm focal length is selected as in the above image

Note: Some CX Surrounds will be using 5.5mm lenses.

The advantage of the 3.5mm lenses is that they have a greater FOV range.

Virtual checker board

Instead of using a large cumbersome checker board to calibrate the stereo cameras,

this method uses a virtual checker board that automatically scales and positions itself depending on the position and image size of the white tube

Note that the CX Surround uses super low distortion lenses so lens bend doesn't have to be taken into account

Although the real distance (d) the ball travels (and thus the ball speed) within the camera exposure time is always measured using RAW LA and Path

(i.e. as measured from the both ends of the ball trace)

it will be more accurate to measure LA and path using fixed launch positions for chipping as by the time the ball is in the FOV of the cameras with slow shots

the ball may well be descending and thus launch angles will be less or even negative if measured from trace ends instead of a known launch position height.

Note that when using a fixed launch position (i.e. when both the RAW LA and RAW path options are switched off)

then the fixed "Ball launch position" has to be set in both the left and right cameras separately

as the left and right cameras will see the launch position in a different places.

Switch RAW Path and RAW LA on/off in camera 2 of the Control Panel

Calibration fine adjustments

Use the Stereo "LA adjust" to fine adjust launch angles (visible in Camera 2)

Use the Stereo "Z adjust LA" to fine adjust the measured Z distance depending on launch angle (visible in Camera 1)

Z distance is the distance the ball traveled forward without vertical launch angle and it directly

effects the actual distance the ball has traveled and thus the measured ball speed.

Use this feature if you find the measured ball speed is decreasing slightly with increasing LA.

Note: You will probably only notice this during the calibration tests when using the calibration card and strip to simulate a ball trace.

Setting up the V and H cams to a stereoscopic system

Select the "Stereoscopic" option in the CP's setup window (top center) and select CX2 mode. (we haven't tested with club tracking yet).

Go to the Vcam window and select "Calibration Mode" and use th f and shift/ f keys to set the camera height value to match your actual camera height from the ground.

Exit the Calibration mode.

Notes: As high lofted flying balls cannot be nearer than 70 cm to the cameras because they will then be out of the FOV, the cameras may have to be moved further towards the player (probably 2 or 3ft or so from the hitting position)

Ensure that both V and Hcams (i.e. left and right cams) have the same exposure time so that ball trace lengths are the same in both cameras.

When testing, ensure that both ends of the ball traces are being detected in both cameras.

Pros and Cons of Stereoscopic vs H cam V cam setups


CX Surround Test Images

A small ship on regular turf carpeting showing a nice bright ball trace.

A faster shot on regular turf carpeting

The ball trace is getting very faint and there's barley enough contrast between the ball and the underlying surface for the system to detect the trace..

Increasing the camera gain helps but this shot was just 62 mph.

At 162 mph the ball trace will be too faint to be detected using regular turf carpeting.

Temporarily laying down some low reflective black carpeting allowed the camera gain to be further increased resulting in a bright ball trace and better contrast.

IBS will probably help with low contrast ball traces though.

Here's the left camera image of the same shot.

Note that - when comparing the two stereo left and right camera images of a shot - it is not possible to determine

the launch angle of the ball just by looking at the images

whereas in the H and V cam setups it is easy.

The side mounted Vcam detects vertical launch angle and speed of the ball

The ceiling mounted Hcam camera detects ball path for normal shots

GSA Golf reseller inquiries welcome

Contact Martin for details





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