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Note: Please ensure you're using CP version 8.6.3.5 or higher for these instructions

Also note that these calibration and adjustment methods are intended for advanced users only

as most are ok with the basic default settings and calibration as supplied with the systems

Above, a customer e-mail from 04/21/2017 regarding the new extended calibration

Factory calibration table set

All current GSA Golf Control Panel versions and updates now include a factory set camera extended calibration table

that negates any user requirement to calibrate the cameras themselves.

see the end of this page for factory calibration details or click the above image


XY camera setup calibration

see further below for our new stereoscopic calibration

Why is calibration or correction required?

With the classic XY camera setup, the Hcam is mounted on the ceiling looking straight down to see the direction of the ball left and right (as shown in the above image)

and the Vcam is mounted at floor level either on the left or right hand side of the enclosure and views the ball in flight from the side. (as shown in the above image)

Note that the Vcam - in addition to measuring the vertical launch angle of the ball - also measures the speed of the ball based on the length of the ball trace.

i.e. The length of the trace is directly proportional to the speed of the ball.

As long as the ball is hit perfectly straight and low, this setup wouldn't require any calibration.

Ball speed and launch angle (LA) accuracy problems occur when the ball is hit either left or right or higher.

This is due to the ball being hit either further away or nearer to the cameras which causes the ball trace images to appear either larger or smaller.

If not adjusted this ball trace size difference will distort the speed measurements.

eg if the Vcam is mounted on the right side and the ball is hit to the right then the ball trace image will appear larger in the camera and thus the ball speed will be measured higher than it actually is.

Likewise, if the ball is hit to the left away from the Vcam camera then the ball trace image will appear smaller and thus the ball speed will be measured lower than it actually is.

Two methods of correction

The two methods of correction are:

1. Full calibration from a pre-defined or user defined calibration table

2. A user defined percentage correction

Full calibration

The full calibration method uses pre-defined calibration tables like the above.

The table contains trace length (i.e. ball speed) and LA correction values for ball paths left and right

The tables are made by actually placing a white pole that represents a ball trace at various angles to the Vcam camera.

In the above table, the camera was placed 5ft away from the center line of the enclosure and the pole is angled left and right in 1 degree increments.

With each increment the measured LA and trace length is measured and recorded. Correction values are then calculated to bring the LA and speed back to their original measurements

Viewing and editing the calibration tables

Click the "Calibration table" option ON to view and edit the calibration tables

The yellow row shows the speed and LA adjustment made for the current shot

In the above example the ball speed was reduced to 91.566% of it's original speed and the LA reduced to 89.429% of it's original LA

The calibration is reducing (instead if increasing) both the speed and LA as the ball path is right - towards the camera - and thus the ball traces will appear larger.

The white row is the row selected by the edit cursor (Use up/down arrow keys to move).

Note that there are 3 sets of tables depending on the distance the Vcam is from the enclosure center line (i.e. 5 ,6 or 7ft)

Also note that the tables are reversed if the Vcam camera is mounted on the left side of the enclosure (Vcam left option ON)

To use this method of correction, switch the Vcam calibration ON in the Vcam window

Note that you can adjust the amount of calibration too

In the above example, speed calibration is reduced to 66% and LA calibration to 101%

Also note that the correct distance the Vcam is from the enclosure center line should be set

In the above example the distance is set to 7ft

In addition, ensure that if the Vcam camera is mounted on the left side of the enclosure, that the Vcam Left option is set to ON

Extended XY calibration

The new XY extended calibration expands this calibration to a 40 degree range (+/- 20 degrees) for 6 launch vertical angle ranges of 10, 20, 30, 40, 50 and 60 degrees.

See the end of this page to read more about Extended Calibration


User defined percentage correction

With the Vcam calibration switched OFF, a user defined percentage correction is used.

In the above example, the camera is mounted on the right side of the enclosure ("Vcam left" option switched off)

In this case the speed of the ball has to be decreased if the ball path is right (i.e. going towards the camera) and the speed increased if the ball is flying left (i.e. away from the camera).

In the above example, the maximum speed increase for a ball flying left has been set to 7.25% and the vertical launch angle (LA) increase set to 6.00%

For a ball flying right (i.e. towards the camera) the max speed decrease has been set to -5.25% and the LA increase set to 4.5%

Note that these percentages are the maximum adjustment which is reached when the ball path is either 20 degrees right or 20 degrees left

If the ball path is 10 degrees then half the adjustment is used and if just 5 degrees then only a 1/4 is used.

Hcam path correction

To-date all calibration and linear adjustments where made for the Vcam camera which is responsible for ball speed and vertical launch angle calculations.

However, the Hcam ball path camera also requires either calibration or linear adjustment in order to calculate true ball path angles.

Calibration tests showed that the Hcam will only detect true ball path angles when the ball vertical launch angle is below 20 degrees.

As the vertical launch angle increases, the ball is getting nearer to the Hcam ceiling mounted camera and lens perspective distortions start to kick in.

Some examples are:

With a true ball path angle of 10 degrees left or right, the Hcam measured path without calibration was:

LA 20 degrees - path angle : 12 degrees

LA 30 degrees - path angle : 15 degrees

LA 40 degrees - path angle : 20 degrees

With a true ball path angle of 20 degrees left or right , the Hcam measured path without calibration was:

LA 20 degrees - path angle : 24 degrees

LA 30 degrees - path angle : 28 degrees

LA 40 degrees - path angle : 40 degrees

As can be seen, high lofted shots can result in ball paths being measured twice as much as they really are. i.e. a real path angle of 20 degrees, is measured as 40 degrees left or right without correction.

To correct this there's a new "Path correction" option in the Hcam window that linearly adjusts the path to it's correct value depending on the vertical launch of the ball.

An Hcam calibration table will be available shortly too

BTW, if you have noticed that some high lofted shots weren't being detected, then it was probably due to the ball path being measured by the Hcam exceeded the "Max ball path" setting in the Hcam window.

Without path correction it would be very easy for the ball path to exceed the limit setting with high lofted shots and then the launch would be declared as invalid.


Other adjustments

Chip speed

Even though the CP measures correct ball speed when chipping, these shots are often too long in the game software.

i.e. the ball travels too far and skips off the green to the other side

To correct this, you can set a ball speed adjustment percentage to reduce the speed of the ball.

In the above example, the speed of the ball when chipping is reduced to 45.00% of the actual measured ball speed.

This speed adjustment will only kick in when the system is in chipping mode and chipping mode will only kick in when the ball is not on the green

but the distance the ball is to the pin is less than the user defined chip distance.

Chip distance

To set the chip distance, hover the mouse cursor over the "Chip distance from pin" text and use left and right mouse clicks adjust the distance.

In the above example the distance to the pin where the chipping mode will be automatically activated is set to 30 yards.

"Min back spin when chipping"

Another major factor when chipping is the measured or calculated back spin

In order to prevent the ball from rolling straight off the green when chipping, the back spin should be quite high.

Use the slider bar to set the "Min back spin when chipping" to at least 4000 rpm

"Spin rate adjustments"

When not using our ball spin cameras, spin rates are calculated from club and ball launch data

Use the spin adjust slider bar to increase or decrease the calculated spin rates.

In the above example, calculated spin rate for all irons has been increased by 135%

Note that spin rate adjustment settings are separate for irons and woods. Hold the shift key down to select irons, otherwise woods are selected.

Hcam path correction

Some small tweeks were made to the Hcam path correction today and the new 7ft calibration table was made with Hcam correction ON.

5ft and 6ft tables didn't use the Hcam correction so will be redone mext week. In the meantime use the 7ft table even if your Vcam is closer or further away.

Chipping mode

When in Chipping Mode, the "min backspin when chipping" slider bar turns into .... "chip ball speed adjust"

and "Launch Angle inc" turns into "Chipping launch angle inc"

Note "Launch Angle inc" is not required when using "Extended Calibration".

"Launch angle ball speed adjustments"

In addition to ball speed adjustments for balls flying left or right, there's also ball speed adjustments related to the launch angle of the ball.

The reason for this is because as the ball flies higher with higher launch angles,

the ball is getting further away from the floor mounted camera and thus the trace length appears smaller

which in turn results in lower speed measurements.

To correct this an "LA Speed" adjustment based on the launch angle of the ball can be set.

In the above example, a max ball speed increase of 16% is set over an LA range of 20 to 60 degrees.

This means that if the ball LA is below 20 degrees then no adjustment will be made but if higher then a percentage of the 16% will be applied to the ball speed.

e.g. If the LA is 60 degrees then the full 16% will applied, if 40 degrees (i.e. halfway between 20 and 60 degrees) then there will only be an 8% (half of 16%) increase.

(BTW the "Cur:" means Current percentage increment used based on the current launch angle of a shot)

Note that if not using this adjustment, high lofted shots may carry too short while woods and long iron carry distances are OK

Also note that this adjustment can be reversed. i.e. the percentage adjustment can be minus and thus the ball speed will be decremented instead of increased with increasing launch angles

Launch angle adjustments (only used when calibration is OFF)

All the calibration work done recently has shown that un-calibrated measured launch angles are far lower than what they really are as viewed by the cameras. Usually around 25 to 30% less

For those that prefer linear adjustments over calibration we've added a linear launch angle adjustment in the Vcam window in this version of the CP

Just click multiple times on the new "Launch angle increase" option to set the LA increment to be 0, 5, 10, 15, 20,25, 30 or 40%

Scaling factor

The CP calculates ball speed by the length of the ball trace of the shot.

A ball trace of a fast moving ball is achieved by using relatively long camera exposure times

In the above example the exposure time (or shutter speed) is set to 10000 micro seconds = 0.01 seconds

The length of the trace in the camera image is in pixels so this length (197 px in the above example) has to be converted to real world length units before it can be used in the speed formula v = d/t

This conversion is done by the user defined "Scaling factor"

In the above example the "Scale" is set to 0.2450 which means each pixel in the image is equivalent to 0.2450 cm

In the above the trace length in pixels is 197 which after conversion is 50.04 cm (i.e. 197 x 0.2450 = 50.04)

After this conversion we can use v = d/t = 0.5/0.01 = 50 meters per second

Setting the base scaling factor

Most just use the default setting of 0.2860 but if you would like to be more exact then the following method should be used.

1. Place a length of white tubing or white pole of a known length in the field of view of the Vcam camera

2. Click the Soft Trigger button to grab a new image in the Vcam window

3. Adjust the scale factor so that the "Distance" is the same as the known length of the pole.

In the above example the tube length is 50 cm and the "Scale" is set to 0.2450 so that the "Distance" is also 50 cm


Individual club carry factors

You can also add speed / carry factors for each club separately in this window

Click the "Carry Factors" button in the CP's Setup window to access this carry factors window.

Note that the "Carry Factors" option has to be set ON in order for them to take effect

There's also a "Driver boost" factor in the Setup window that just adjusts ball speeds for Drivers


Stereoscopic camera calibration

Stereoscopic vision camera software for your GSA Golf CX camera systems will be available soon

Release date for this free software update is scheduled for the end of April 2017

As an alternative to the standard X,Y camera setup for CX camera systems,

the new stereoscopic image processing software will allow you to mount both ball tracking cameras on the ceiling instead of one on the ceiling and the other on the floor.

Note that there will be a standard default calibration for stereoscopic camera setups that won't require any user adjustment for basic play

Two 3d co-ordinates of the ball trace are captured with stereoscopic camera setups

Formulas are used to determine speed, direction and launch angle of the ball

Stereoscopic theory

Which is better: XY or Stereoscopic?

In regards to ball tracking in a golf simulator, at present there's still a debate as to which method is more accurate.

Certainly XY setups are as accurate - if not more so - than stereoscopic setups providing there is sufficient calibration.

Our current tests actually show that there are issues with short spacing parallel stereoscopic setups with low shots.

i.e. it's ability to differentiate between a low shot and a ball skimming or rolling along the ground

whereas XY setups have no problem with this.

Also a major drawback with stereoscopic setups is the fact that the user cannot easily see the vertical and horizontal launch data simply by looking at the captured images.

In contrast to XY setups - that clearly show vertical ball launch angle and ball path in the captured images - the camera images in a stereo setup won't make much sense to the average user.

Aligned and angled camera positions

In contrast to the parallel stereo camera setup where the cameras are only spaced at around 1 ft from each other and point straight down,

current tests are showing far better results when the cameras are spaced at greater distances (6ft or more) and angled to and aligned to a base center point as in the above image.

Calibration methods

Note that there will be a standard default calibration for fixed camera spacing and mounting heights so that no additional calibration will be required by the user.

The calibration method consists of placing a large chequered image printout mounted on a board directly under the cameras at various heights.

Each square on the board represents a golf ball position at various positions in 3D space.

Note that if we didn't use a chequered board, we'd have to place hundreds of golf balls under the cameras at precise positions - a near impossible task.

The board is first placed at ground level and the cameras are triggered (via a soft trigger in the CP) to capture the image in both cameras.

Each square's XY position in both left and right cameras is recorded together with the real 3D XYZ position of each square.

The procedure is repeated 20 times while raising the board 10 cm upwards with each step for each area segment.

Total height is then 200 cm ( 6.5ft)

Note that the size of the chequered board has to be entered into the CP's stereo calibration window before this procedure is started

together with the real 3D position of the board itself.

The number squares on the board is automatically detected but if insufficient squares are available for the entire scan area

(usually 4ft X 4ft ) then multiple scans will have to be made to cover this area.

Precise and level method of raising the chequered board under the cameras during the calibration process

The calibration creates a 3D matrix that converts XY ball pixel positions in the camera's 2D images into real 3D XYZ positions

Note that it is unlikely that the ball will be captured by the cameras exactly on a specific X,Y,Z 3d co-ordinate in the matrix

but it will be surrounded by 8 of the nearest 3d co-ordinates.

These 8 3d co-ordinates are used to determine the exact ball position within those co-ordinates and finally the exact position in 3d space

These real XYZ co-ordinates are then used to calculate precise ball launch angle, speed and path

 

This stereo calibration feature will be available in the CP within the next 2 months or earlier

Note that there will be a standard default calibration for fixed camera spacing and mounting heights so that no additional calibration will be required by the user.


Extended XY Calibration

for V and H cam camera setups

Note that there will be a standard factory set extended calibration for XY camera setups but if you'd like calibrate your system yourself then this is how

The V and Hcam calibration method involves using a black or dark long rod with a movable white plastic tube or paper roll attached to one end

and pinned down at the other end with a swivel mounted on a base plate at the usual ball hitting position on the hitting mat.

A swivel speaker mount (like the ones used for the camera mounts) attached to the rod end works very well for this

The base plate will have to be attached to the flooring somehow if it is too small or not large and heavy enough.

Double sided tape works well if mounted on a flat smooth floor surface. Otherwise the base plate has to either be weighted down or increased in size so the rod base does not lift up.

The rod is tilted upwards in 10 degree steps from 10 degrees to 60 degrees to simulate various launch angles of the ball

and moved both left and right in 2 degree steps to simulate ball path from 20 degrees left to 20 degrees right.

The total number of entries is then 21 x 6 = 126

A tilt meter is used to measure the real angle of the rod and the Hcam is used to measure the ball path.

Slide the white tube up or down as necessary to keep it in the same FOV of the camera with every step. This simulates the same trigger point.

Use blocks of some kind (e.g. stools or chairs etc) under the rod to support the rod at the desired angles.

Use the Hcam to check the desired ball path

Start at Vertical angle of 10 degrees and zero degree path and set the scaling factor so that the distance measured in the Vcam is the same as the actual length of the white part of the rod

Move the rod right 2 degrees and soft trigger to capture new images of both the H and Vcams

The above image shows the new extended calibration table.

There are 6 pages for launch angles (LA) from 10 to 60 degrees in 10 degree steps

Each page consists of 21 LA and Speed adjustment rows for ball paths in the range of -10 to + 10 degrees in single degree steps

(You can also set the path range to -20 to +20 degrees by switching the path steps to 2 degrees)

During the calibration process a ball launch angle, ball speed and ball path will be calculated from the pole

Use the page up and page down keys to select the LA range of the shot

In the above example LA was 14.55 degrees so the range 10 to 20 is selected

You should then see the entry in the table that is used to adjust the LA and Speed for this particular shot (or pole placement)

Move the row cursor to the active entry and press the "E" to edit

Adjust the speed and LA correction factors until the length of the white rod length measured in the Vcam window is the same as the real length

and the measured Launch angle is the same as the real launch angle as read from the tilt meter.

Press the ESC key to exit Edit Mode

Continue the process until all 120 LA and Path position entries have been made.

Note that this calibration method uses the new "Extended" calibration feature so ensure that you have the "Extended Calibration" option ON

Also note that when calibrating, ensure that all other speed and LA adjustments are off.

i.e. Carry factors are set to OFF.

and LA speed inc / dec is set to zero percent

as these adjustments will no longer be required after calibration

 

Note that there are a number of new features in the Vcam window.

1. Raw speed is now shown. Raw speed is the speed calculated from the camera without any adjustments or calibration

2. A Darken image option is now available that darkens the Vcam image so thet the calibration table is more readable.

3. Calculated trace length distance is now shown in a pink shade so that it stands out more


Auto calibration

With the auto calibration mode ON, the calibration process will automatically set the trace distance and LA corrections for you.

All you need to do is place the pole at the -20 to +20 degree path angles in the Hcam window - which will automatically be set in video stream mode - then switch to the Vcam.

After switching to the Vcam window, the adjustments will be automatically calculated and and you're ready to go back to the Hcam window again for the next path angle and/ or launch angle.

Total calibration time in this mode should be less than 30 minutes for all 126 launch angle and path calibrations

Ensure the following when using Auto Calibration

1. Vcam calibration option is ON

2. Extended calibration option is ON

3. The base trace length is set to the real length of the white tube

4. Auto Calibration adjust option is ON

5. The LA range is set to the vertical angle of the white tube

6. The Vcam calibration percent is set to 100 pecent for both speed and LA

Calibration procedure

1.Start with LA range 0 to 10 degrees and switch to the Hcam window

You will see that the Hcam is already in video stream mode.

2. Move the pole to zero degrees path. The path angle of the pole will automatically be shown in degrees as you move the pole left and right.

And the vertical angle to 10 degrees or a little less by placing a support under the pole

3. Switch to the Vcam. You should now see that the LA is automatically set to 10 degrees and trace length to your base trace length.

4. Switch back to the Hcam and move the pole right until the Hcam shows 2 degrees right

5. Switch back to the Vam

Repeat this process for all degrees right and left i.e. moving in 2 degree steps from 0 degrees path to +20 degrees right

and from zero to -20 degree left

Once complete, adjust the pole to 20 degrees and use the page up/down keys to go to the 10 to 20 degree range.

Start the left right pole path procedure again.

Repeat for vertical pole angles of 10, 20, 30 ,40 and 60 degrees

The end result of this calibration should be absolute consistency across the entire vertical and horizontal range

from 0 to 20 degree ball paths left and right and launch angles from 0 to 60 degrees

Auto calibration mode - now even faster

To speed up calibration even further, you can switch between the Vcam and Hcam by simply pressing the "Space" bar on the keyboard.

This saves you the time it would normally take to switch cameras with the mouse.

And instead of having to look at the screen to see if the auto calibration worked for each angle step every-time, there's now an audible beep that tells you all is OK.

Calibration Example

The above shows a typical calibration table

In this example, the pole was angled at 30 degrees vertically and 20 degrees left.

The white tube on the pole - i.e. the part that represents the ball trace - was 56cm in length

Without calibration the launch angled measured by the camera was only 23.41 degrees. The correction value was automatically set to 1.28 in order to measure the true launch angle of 30 degrees

The trace length measured by the camera was smaller than the 56 cm so the correction value was automatically set to 1.032.

The trace length dictates the speed of the ball and before calibration the measured speed (Raw speed) was only 121.45 mph. After calibration. speed was up to 133.4 mph.

Here the Hcam is being used to measure the ball path angle during the calibration process

Note that Hcam "ball path correction" has to be switched on in order to use the Hcam to measure ball paths accurately

If not using the Hcam to measure the path of the pole then a plum line

suspended from the pole beginning over a large protractor will have to be used to measurre exact pole paths

Note that the pole end was placed on a rail on boxes and tables to hold the vertical angle of the pole

Calibration process tips

1. When setting the pole vertical angle, ensure that the angled measured with the tilt meter is no greater than the selected vertical range.

e.g. when selecting a launch angle range of 10 to 20 degrees, set the pole to 20 degrees and no more

when selecting a launch angle range of 20 to30 degrees, set the pole to 30 degrees and no more and so on

2. When moving the pole left and right in the 2 degree steps to simulate the ball path, ensure that the complete white part of the pole is detected in the Vcam

and that the measured raw vertical launch angle stays below the LA range max.

e.g. if the range is 20 to 30 degrees then the raw angle (i.e. the angle without calibration ) is no greater than 30 degrees

3. With every step, ensure you hear the audible beep when pressing the space bar to get back to the Vcam from the Hcam

Current CP calibration updates include:

1. Pressing the Z key resets the calibration on the active row to zero calibration (i.e. 1.0 correction factor)

2. Pressing the ESC key closes the calibration table

3. An index check is made with each auto calibration step to ensure that the correct table is being accessed

No beep is played if index is not in the correct range or when any other error occurs during the calibration process


Factory calibration table set

All current GSA Golf Control Panel versions and updates now include a factory set camera calibration table

that negates any user requirement to calibrate the cameras themselves.

The table consists of 3 calibration tables each consisting of 126 entries

for various distances the Vcam is from the center line

Vcam distances from the center line are 5ft, 6ft and 7ft.

Note that the calibration table "calibLRex.csv" is placed in the "C:\Program Files (x86)\GSAControlPanel\data" folder when you download the latest CP update.

In order to use it, the new "Factory Calibration" option must be on.

Any user calibration tables won't be overwritten when this option is on but if you would like to edit the factory tables then switch the "Factory Calibration" option OFF again before editing.

The table will then be automatically saved to the "C:Users\Public" folder.

Calibration factors used now displayed

The calibration factors used for the current shot are now displayed in the Vcam window.

These are Speed adjustment, Launch Angle (LA) adjustment and the index number into the calibration table.

In the above example, the raw speed of the ball was reduced to 84% and the raw LA increased by 38%

Extended calibration "Scale" factor = 0.2780

Note that the Scale factor for the calibration tables was set to 1 pixel = 0.2780.

This scale factor used with the calibration tables should result in exact ball speed measurements across the entire 0 - 60 degree launch angle and +/- 20 degree path range.

Increasing or decreasing this scale will result in decreased or increased measured ball speed across the entire range should you care to change it.

Don't forget !

If your Vcam is mounted on the left side of the enclosure, ensure that the "Vcam Left" option is ON

otherwise your calibration will be reversed

Also don't forget to set the distance your Vcam is from the enclosure center line

Currently distances are 5ft, 6ft and 7 ft.

If your Vcam is over 7 ft away from the center line then just use 7ft setting for now.

Other distances will be available later this year

Also don't forget to set the amount of calibration to 100% for both speed and LA to start with

Later you can reduce or increase the amount of clibration for both Speed and LA to suit

In the above example the speed calibration was reduced to 50% so that any ball speed adjustments for ball hit left or right will be 50% less

Note that the calibration tables where made with a ball to trigger distance of 5ft.

Later next month we'll have exact speed calibration percentages for various other ball to trigger distances

Also don't forget to set "Extended Calibration" ON and "Factory calibration" ON

Note that these are default ON with the new CP releases

And finally, don't forget to switch "Carry factors" OFF

 

and "Ball speed controls" to their default of 100%


Calibration kit

For those that wish to calibrate their cameras themselves, a calibration kit is available.

The calibration kit consists of a telescopic pole that extends to 15ft, a white tube, a pole base and hinge.

Price is $199