Difference between ROS topic /left_cam_imu_transformation and Kalibr cam_imu extrinsics results

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Description

Dear Sir,

I'm using Zed2i's sensors (left camera and IMU) with an external monocular VIO pipeline. The extrinsics I receive from the ROS topic /left_cam_imu_transformation and from Kalibr are very different.

The extrinsics from /left_cam_imu_transformation is: rostopic echo /zed2i/zed_node/left_cam_imu_transform translation: x: -0.0020000000949949026 y: -0.023000003769993782 z: 0.0002200000308221206 rotation: x: -0.0010500885546207428 y: -0.0 z: -0.00393286207690835 w: 0.9999917149543762 which is equivalent to - [0.999969, 0.007864, -0.000099, -0.002000, -0.007864, 0.999967, 0.002121, -0.023000, 0.000116, -0.002120, 0.999998, 0.000220, 0, 0, 0, 1]

While the extrinsics from Kalibr (https://support.stereolabs.com/hc/en-us/articles/360012749113-How-can-I-use-Kalibr-with-the-ZED-Mini-camera-in-ROS-) are : cam0: T_cam_imu:

[-0.004248117180815025, -0.9998625130142822, -0.016028367639358054, 8.41951564249623e-05]
[0.001063559295260974, 0.0160239856188632, -0.9998710420481793, -1.708597954171419e-06]
[0.9999904111250486, -0.004264616471714999, 0.0009953413010867496, 3.811715513237331e-06]
[0.0, 0.0, 0.0, 1.0] cam_overlaps: [1] camera_model: pinhole distortion_coeffs: [0.0006582543326556634, -0.001338594740114625, 0.0003683086103016461, 0.0016571045464767074] distortion_model: radtan intrinsics: [662.3788576876452, 662.6400636208534, 654.9267980662693, 366.0819275708851] resolution: [1280, 720] rostopic: /zed/zed_node/left/image_rect_color timeshift_cam_imu: 0.10015660064007245 (also strange)

In addition, while the camera is horizontal and facing forward, the output of /zed2i/zed_node/imu/data_raw is: header: seq: 17969 stamp: secs: 1681195935 nsecs: 453395218 frame_id: "zed2i_imu_link" orientation: x: 0.0 y: 0.0 z: 0.0 w: 0.0 orientation_covariance: [-1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0] angular_velocity: x: -0.058271501732520346 y: -0.1356413144708724 z: 0.06934011135360624 angular_velocity_covariance: [6.595000957109997e-10, 0.0, 0.0, 0.0, 1.9613346042712762e-09, 0.0, 0.0, -0.0, 7.858832729846918e-10] linear_acceleration: x: 1.5133049488067627 y: 0.3734425902366638 z: 9.75547981262207 linear_acceleration_covariance: [0.007840245962142944, 0.0, 0.0, 0.0, 0.008192301727831364, 0.0, 0.0, -0.0, 0.007778662722557783]

You can see the z axis of linear_acceleration is pointing up. According to /left_cam_imu_transform it should be pointing forward (like the camera).

Please advise.

Thank you, Yoni

Steps to Reproduce

rostopic echo /zed2i/zed_node/left_cam_imu_transform
Follow https://support.stereolabs.com/hc/en-us/articles/360012749113-How-can-I-use-Kalibr-with-the-ZED-Mini-camera-in-ROS-
rostopic echo /zed2i/zed_node/imu/data_raw

Expected Result

Transformation should look similar

Actual Result

Transformation not similar

ZED Camera model

ZED2i

Environment

ROS Noetic on Ubuntu 20.0 on an intel chip (Lenovo Thinkpad)

Anything else?

No response

stereolabs / zed-ros-wrapper