Orientation of IMU in different OAK models

Letty

I found old posts related to the IMU orientation, but not specifically what I'm looking for.

I used different models of OAK-D cameras, specifically old USB and PoE OAK-D (gen 1), and I used the raw accelerometer on the IMU to find pitch and roll angles after converting the axis orientation to the coordinate reference system that I use.

I recently purchased an OAK-D lite and noticed that the axes on the IMU seem to be orientated differently, so that to obtain the results I need to convert them in a different way to what I used before.

These are the orientations from what I could determine by looking at the raw accelerometer values (excuse my crude drawing, the box on the left is supposed to represent a generic OAK-D camera facing in the viewer direction)

Is this a difference between all gen1 and gen2 models with IMUs? Is there a way to know how the IMU is oriented when connecting to the camera?

erik

Hi @Letty ,
On newer devices (manufactured in last ₆ months), we also flash imu extrinsics to the device, and you can query them via:

    calibData = device.readCalibration()
    print(calibData.getImuToCameraExtrinsics(dai.CameraBoardSocket.CAM_A))

ATM it doesn't seem it auto-populates (from device name/revision) these extrisnics if they aren't flashed in calibration, but I believe this is WIP. Let me ask the team. You can find them in depthai-boards repo, example:
luxonis/depthai-boardsblob/main/boards/OAK-D-LITE.json#L53
Thanks, Erik

Letty

erik That's great info, thanks a lot!

stanislawix

Is there any way to obtain the OAK-D's or specifically BW1098OBC model's IMU extrinsics? I don't see them in here: luxonis/depthai-boardsblob/main/boards/BW1098OBC.json , neither in luxonis/depthai-boardsblob/main/boards/OAK-D.json 🙁

OskarSonc

Hey stanislawix - Hi,

You’re not missing anything in those JSONs, the older OAK-D / BW1098OBC IMU extrinsics are not currently published there yet, but they should be available in an upcoming update soon.

For now, I can provide the rotation for OAK-D / BW1098 R1M0E1 with BNO086:

[[-1, 0, 0],
 [ 0,-1, 0],
 [ 0, 0, 1]]

Equivalent Euler rotation:

r=0, p=0, y=180

So X and Y are flipped, while Z stays the same.