Camera Calibration on a Computer

This page describes how to calibrate Skynode's camera using a calibration tool on a connected computer.

Installing the calibration tool

The calibration tool is available in a virtual machine. We recommend using it on either a Windows 11 or Ubuntu host machine.

Please contact Auterion to receive a download link for the necessary software.

Virtual machine installation

Installing the virtual machine requires 20GB of free storage on the host machine.

1. Download the Ubuntu22.ova file provided by Auterion. Note that this is a large file: approximately 7GB.

2. Download and install VirtualBox.

   1. Download the latest version for your host machine from https://www.virtualbox.org/wiki/Downloads.

   2. Install VirtualBox by double-clicking the downloaded file. Follow the installation prompts, using the default settings.

   3. Restart your computer after the installation if prompted.

3. Launch the newly installed VirtualBox application. A shortcut should be visible on your desktop as Oracle VM VirtualBox.

4. Import the virtual machine.

   1. In VirtualBox, go to File > Import Appliance….

   2. In the window that appears, click and select the Ubuntu22.ova file provided by Auterion.

   3. Click Next, then click Finish to start the import process.

      This process might take a few minutes, and you’ll see a progress bar labelled Importing appliance….

   4. Once the import is complete, you will see Ubuntu 22.04 listed in the left sidebar of VirtualBox.

5. Start the virtual machine.

   1. Click on Ubuntu 22.04, then click Start to launch the virtual machine.

   2. When prompted, select the user auterion.

   3. Enter the password auterion.

6. On the desktop, you will now see two files:

   1. AuterionCameraCalibration.AppImage

   2. calibration_settings.env

Ubuntu 22.04 installation (advanced)

Some users with Ubuntu 22.04 machines may wish to install and run the calibration tool without using a virtual machine. The steps for this advanced installation are described in the section below.

Advanced installation

1. Install ROS 2 Humble. We recommend using the binary packages.
2. Extract the calibration tool ZIP file provided by Auterion to a convenient location on your machine. There should now be two files in the same directory:

   1. AuterionCameraCalibration.AppImage

   2. calibration_settings.env

Performing a calibration

Start by preparing the calibration target, then run the calibration tool.

The calibration process should take around 1 to 2 minutes.

Prepare the calibration target

Download and print the checkerboard calibration pattern in the PDF file below and mount it to a flat, rigid surface.

Measure the width of one square as accurately as possible. If printed on an A4 page, the width should be close to 25mm (0.025m).

88KB

Checkerboard-A4-25mm-8x6.pdf

pdf

Double-click and open the calibration_settings.env file distributed with the calibration tool. Set the value of SQUARE_WIDTH to the measured square width in millimetres and save the file.

Prepare Skynode

1. Ensure that the video2ros app is installed on Skynode. If not, you can download and install it from Auterion Suite.

2. Open the apps page of the Skynode web UI at http://10.41.1.1/apps.
3. Open the settings for the video2ros app, under System Services, by clicking the gear icon and then Settings.

4. Set Use Custom Auto Exposure to false, and click Save.

On Skynode X and Skynode ENT, the gst-ros-bridge app is also required. Please contact Auterion to obtain a copy of the app and for further assistance.

Start the calibration

Ensure that the square width is correct in calibration_settings.env (see above), then double-click on AuterionCameraCalibration.AppImage to open the calibration tool.

A window will appear with the video stream from the camera. Hold the checkerboard in front of the camera such that the entire pattern is visible in the image. If the pattern is recognised, a multi-coloured grid will be drawn on the checkerboard.

Move the checkerboard around in front of the camera, keeping the entire pattern visible. Data must be captured with the pattern at different positions and orientations:

1. at the top and bottom of the image,

2. at the left and right sides of the image,

3. near and far from the camera, and

4. with different angles of skew (where one corner of the pattern is closer to or further from the camera).

The coloured bars to the right of the image will indicate how many images have been captured at each of these positions. They will turn green when sufficient data has been captured.

Once the data capture is complete, the Calibrate button will turn green. When ready, click this button to compute the calibration parameters for the camera and generate a calibration file from them.

If the calibration is successful, the calibration file will automatically be uploaded to Skynode and you can close the calibration tool.

If the calibration is completed but reports a poor calibration result, we recommend restarting the calibration. Close the calibration tool and ensure that the calibration pattern is flat, the square width is correct and the camera lens is clean before restarting.

Restore Skynode to its original state

1. Open the apps page of the Skynode web UI at http://10.41.1.1/apps.
2. Open the settings for the video2ros app, set Use Custom Auto Exposure back to true, and click Save.