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ethz-asl / kalibr

The Kalibr visual-inertial calibration toolbox
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Reference Frames used in the calibration #322

Open frme92 opened 4 years ago

frme92 commented 4 years ago

Hi, I'm a student using Kalibr with a Pointgrey camera and a 3DR Pixhawk Imu. Could someone tell me which reference frames are used in the calibration? From the information found, it should be the Imu reference frame oriented with z-axis downwards, x-axis backward and y-axis to the left. Instead the one of the camera has a z-axis directed along the axis of the optics while the x-axis towards the right and the y-axis downwards. Finally the world reference frame has x and y axis in the target plane with the first to the right and the second to the top. And then the z-axis coming out of the plane. it's correct? If yes, what sequence does the rotation matrix T_ci use? 3-2-1 or 1-2-3?

kannidekan commented 4 years ago

execuse me, do you know how could i get the IMU YAML file of the requirements in the camera-imu calibration? #341

Thanks very much!

frme92 commented 4 years ago

Yeah, as shown in https://github.com/ethz-asl/kalibr/wiki/yaml-formats, what you're looking for is a .yaml file like this:

Accelerometers

accelerometer_noise_density: 1.86e-03 #Noise density (continuous-time) accelerometer_random_walk: 4.33e-04 #Bias random walk

Gyroscopes

gyroscope_noise_density: 1.87e-04 #Noise density (continuous-time) gyroscope_random_walk: 2.66e-05 #Bias random walk

rostopic: /imu0 #the IMU ROS topic update_rate: 200.0 #Hz (for discretization of the values above)

If you're lucky you can find those values in your IMU data sheet, otherwise you need to do an Allan Variance as shown in https://github.com/ethz-asl/kalibr/wiki/IMU-Noise-Model. In the latter case, if you have a Matlab license there's a very useful toolbox in this page: https://github.com/rpng/kalibr_allan