How can I know what camera calibration consists of?
In other words, what is considered in this process?
I looked for documentation on the Internet but I didn’t find anything. I only found something about the reasons why calibrate is necessary and similar, but this is not what I want to know.
Thank you
maybe I was thinking about autotuning algorithm to calibrate the sensors. How does it work?
Hi @Paolo
camera calibration is a Computer Vision process required to create a mathematical model of the camera optics:
https://docs.opencv.org/2.4/modules/calib3d/doc/camera_calibration_and_3d_reconstruction.html
We provide these parameters within the ZED SDK thanks to our factory calibration procedure performed with precise robotic arms:
https://www.stereolabs.com/docs/video/camera-calibration/
I am sorry, I am interested in IMU sensor calibration and not camera calibration
For IMU sensor calibration you can use the Kalibr tool.
We provided a guide in the support section of the website to use it, it’s an old guide, but the main concepts are still valid:
I try to explain it better.
When I switch on my zed2i camera I have to a few minutes to let the sensors calibrate themselves.
During this period an autotuning algorithm is used to calibrate the sensors and I would like to know what this algorithm does.
Keeping the camera steady and fixed on the floor, how does it calibrate the sensors?
Thank you
Ah ok, this is a very easy algorithm.
The gyroscope sensors have an intrinsic systematic error called “bias”.
There are 3 biases, one for each axis, that change when the temperature of the sensor change.
So when you start to use the camera and the temperature increases the 3 biases change until the temperature reaches a stable level.
The ZED SDK is designed to measure the values of the biases and internally store the averages of the bias of each axis, so it can remove it from the acquired values and provide a stable measure of the angular speeds of the camera.
ok, thank you.
So the waiting time is only due to gyroscope biases and not to accelerometer biases too?
Exactly, it’s only an angular velocities issue.
I have another question.
I saw it’s available the terminal command "ZED Sensor Calibration.exe" --cimu to reset the biases values.
When is this operation necessary? Is it good to do this every time I switch my camera on? Or are there any specifics moments to do this?
Thank you so much
That’s required only if the camera orientation continues to drift even after the warmup.
For the ZED2i it simply removes the bias values stored in the internal EEPROM of the camera.