Troubles with T265 IMU coordinate system.

[alejandronespereira]

Required Info
Camera Model	t265
Firmware Version	5.15.1
Operating System & Version	Ubuntu 22.04
Kernel Version (Linux Only)	(e.g. 4.14.13)
Platform	PC
SDK Version	6.20.0-36-generic
Language	C++
Segment	Robot

Issue Description

I am having trouble wrapping my head around the t265 IMU coordinate system. I am trying to integrate the IMU data as well as the odometry produced by the tracking camera. I see in the official documentation here that the coordinate system is a Right Hand convention with the Z pointing inwards the camera, and Y point upwards.

However, the ROS2 wrapper is outputing the IMu in a frame that does not exist on the tf that is published, camera_imu_optical_frame. i will refer to the axes denoted on this image:

as XYZ (in caps) from now onwards, and the gravity vector G as pointing towards the ground.

Here are the values for the linear acceleration depending on the camera orientation:

• X = G (side of the camera with the USB connection facing the ground):
  x: 9.8, y: 0, z: 0
• Y = G (camera upside down):
  x: 0, y: -9.8, z: 0
• Z = G (camera facing the sky):
  x: 0, y: 0, z: 9.8

I don''t understand why the Y axis is negative, but again the camera_imu_optical_frame has no connection to the camera that I know.

What am I missing?

[JTShuai]

@alejandronespereira Hi, I have the same trouble. Have you found any updates on it?

[alejandronespereira]

Nope, sorry. I recall I ended up publishing some tfs myself and taking those into account for a while, but as the camera is discontinued I ended up with another solution that did not use this model.