In which frames is the IMU data expressed?

[stephane-caron]

The IMU field in the observation dictionary contains data like so:

{
  "linear_acceleration": [
    0.0079445635178187,
    4.439796721811672e-06,
    0.00017145108524911683
  ],
  "angular_velocity": [
    1.1916298054173672e-05,
    -0.018927168979633598,
    1.3641552245686093e-05
  ],
  "orientation": [
    -1.1888706467289014e-05,
    0.0048754503950476655,
    2.35814877669327e-06,
    0.9999881386756897
  ]
}

What are the units and in which frames are these quantities expressed?

[stephane-caron]

These three fields are listed in the ImuData class from Vulp. As documented there, both velocities are body vectors expressed in the IMU frame. For similar questions, check out the Observations listing in the documentation.