Camera Calibration on Skynode

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

Running the calibration on Skynode is slower than running it on a connected computer. Where possible, we recommend running the calibration on a computer.

Camera Calibration on a Computer

Required apps

Open the Apps page of the vehicle web UI on http://10.41.1.1/apps and ensure that the video2ros and camera-calibration-service apps are installed.

These can be downloaded from Auterion Suite: video2ros, camera-calibration-service

Before calibrating

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).

Checkerboard-A4-25mm-8x6.pdf

PDF · 88KB

Open

Configure the calibration service

Open the Apps page of the vehicle web UI on http://10.41.1.1/apps and find the camera-calibration-service app. Click the gear icon and select Settings. Set the values as follows, then click Save.

Setting	Value	Description
Camera Topic	/camera/image_raw	Camera topic from which to receive images. camera/image_raw is the default for images from the video2ros app.
Calibrate Camera	1	Boolean flag, whether the calibration task should be run. Set to 1 to perform calibration.
Pattern	chessboard	The pattern used for camera calibration. Only the chessboard pattern is currently supported.
Size	8x6	Number of inner corners on the chessboard (width x height). The order of width and height doesn't matter (8x6 = 6x8). On one axis, this is number_of_squares-1 .
Square Size	<for example: 0.025>	Width of one square on the checkerboard, as measured above, in metres.

Configure video2ros

Open the settings for the video2ros app, under System Services.

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

Stop all other apps

To ensure the calibration runs smoothly, only the camera-calibration-service and video2ros apps must be running.

On the Apps page of the vehicle web UI, stop all other apps by clicking the gear icon and then Stop.

Perform the calibration

Click the video2ros app's blue Add calibration file button to open the calibration webpage. Check the Show Calibration Tool checkbox and - when you are ready - click the Start Sampling button to begin recording calibration data.

A window will appear with the video stream from the camera. Position the checkerboard 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.

The calibration video stream in which the checkerboard pattern has been recognised. On the right, the coloured bars show the coverage of different positions in the recorded calibration data.

Once the data capture is complete, you will be prompted to click Calibrate. This will compute the calibration parameters for the camera, generate a calibration file from them, and save the file on Skynode.

Restart the video2ros app for the new calibration file to be applied.

Restore all apps after calibration

Skynode should be restored to the state it was in before the calibration procedure was performed.

1. Stop the camera-calibration-service app and disable auto-start.

2. In the video2ros app settings, set Use Custom Auto Exposure back to true.

3. Restart all other apps.

Ensure that the camera-calibration-service app has been stopped and auto-start disabled.