Issue about the global frame

[Mrzhen-wz]

Hi Mr.Brossard,
I'm very interested in your paper called Denoising IMU Gyroscopes with Deep Learning for Open-Loop Attitude Estimation.
I have a little question. In your paper,the rotation matrix Rn at timestamp n maps the IMU frame to the global frame. Does the global frame in your paper mean the geographical coordinate system ? or geocentric coordinate system ?

Thanks!