LED Stage Synchronization

Before presenting content on an LED stage with AR-51, you may want to synchronize AR-51’s coordinate system with the LED system.

This ensures a consistent origin across sessions and allows direct alignment with LED walls or floors.

Table of contents

1. Motivation
2. Using AR51’s Aruco Style checkerboard pattern
   1. AR51 Server Settings
   2. Projecting the Checkerboard
3. Using AprilTag Style checkerboard pattern
   1. AR51 Server Settings
   2. Projecting the Checkerboard
4. Rescaling the Checkerboard
5. Handling Coordinate Offsets

Motivation

You want to present something on the LED stage and synchronize AR-51 with another system.
Examples include:

• Use your body to control the content that is displayed on the LED wall/floor.
• Ensuring the AR-51 origin is placed consistently in the same spot each time.

Using AR51’s Aruco Style checkerboard pattern

AR51 Server Settings

• In the AR-51 server settings:
  • Navigate to:
    Camera Calibration Settings → Checker Board Settings → Calibration Method
  • Select Charuco from the dropdown menu.
    
  • • Navigate to:
      Camera Calibration Settings → Checker Board Settings → Board Square Count

  • Set Board Square Count to reflect your number of corners on the board (8x5 in the attached file, note this is the corners not the actual squares count).

    

  • Save the server settings if you want this to persist.

Projecting the Checkerboard

To sync AR-51 coordinates with the LED stage:

1. Project the provided checkerboard image onto the LED floor.
   • Download the checkerboard image
   • The small mark at the center of the checkerboard indicates the AR-51 origin.
2. AR-51 uses a right-hand coordinate system where Y is up.

Using AprilTag Style checkerboard pattern

AR51 Server Settings

• In the AR-51 server settings:
  • Navigate to:
    Camera Calibration Settings → Checker Board Settings → Calibration Method
  • Select AprilTags from the dropdown menu.
    
  • Navigate to:
    Camera Calibration Settings → Checker Board Settings → Board Square Count

  • Set Board Square Count to reflect your number of squares on the board (15x10 in the attached file).

    

  • Save the server settings if you want this to persist.

Projecting the Checkerboard

To sync AR-51 coordinates with the LED stage:

1. Project the provided april tags image onto the LED floor.
   • Download the april tags checkerboard image
   • The center of the board is AR-51’s system origin.
2. AR-51 uses a right-hand coordinate system where Y is up.

Rescaling the Checkerboard

• Measure the a calibration square in the “real world” When you measure your “real world” checkerboard square make sure to measure the entire square - Not just the inner aruco area. You can also measure the pattern from side to side and divide by the number of squares for better accuracy.

Standard Calibration Board	AprilTags Calibration Board

• You may rescale the checkerboard, but it must be uniform so that each square remains a square.
• In the AR-51 server settings:
  • Navigate to:
    Camera Calibration Settings → Checker Board Settings → Aruco Board Square Size Meters
  • Enter the real-world size of a checker square (in meters).

When you measure your “real world” checkerboard square make sure to measure the entire square - Not just the inner aruco area. You can also measure the pattern from side to side and divide by the number of squares for better accuracy.

Handling Coordinate Offsets

If the LED coordinate system is not centered on the stage (e.g., origin is in the upper-right corner), you can adjust using:

• Camera Calibration Settings → Calibration Checkerboard Offset
• Set the offset values so AR-51 matches the LED system’s origin.