Hi Stereolabs team,
i am using a ZED i2 and i need the following parameters:
-accelleration bias random walk
-gyroscope bias random walk.
If it is possible i need the reference frame of imu with respect to zed_camrera_link or zed_camera_center.
Thank you for your help
Hi Francesco,
Both values are available through the SDK, so the reliable way to get them is to read them from your own camera rather than from a datasheet. They sit in getCameraInformation().sensors_configuration, as accelerometer_parameters.random_walk and gyroscope_parameters.random_walk, with the unit in sensor_unit.
These two values are defined per IMU model, not per unit, so every ZED 2i returns the same figure for instance. The field is NAN when the camera does not provide it, and the gyroscope is in degrees, so convert to radians before feeding Kalibr or an EKF.
The IMU to camera transform is calibrated per unit and comes from the same structure, as camera_imu_transform. Its reference is the left camera, not the camera center. In ROS 2 the wrapper publishes left_camera_frame to imu_link, and the same transform on the left_cam_imu_transform topic. A tf2 lookup from zed_camera_center to zed_imu_link resolves, but only if you launch with publish_imu_tf:=true, which is false by default.
For better accuracy you can recompute the parameters with an Allan variance over a long static sequence, more than six hours, using ZED_Sensor_Viewer to grab the raw data.
Best regards,
Tristan Leduc