question about the variable avgA in class IMU::Preintegrated

[Cai-RS]

Hello, thanks for your great work! I found that in Tracking::StereoInitialization() function, the two variables avgA of mCurrentFrame and mLastFrame are compared to decide whether the acceleration between first 2 image frames is enough.

However, it seems that variable avgA is the (time) weightd average of IMU acceleration data (have to subtract the bias) between every two images (image A and image B), and it is in the IMU coordinate system at the initial moment of the pre-integration (that is, the moment of image A).

So the problem is, how to subtract two vectors that are not in the same coordinate system? Did you forget to transform avgA to the common coordinate system (for example, the IMU coordinate system at the moment of first image in all system)?

[WFram]

All the accelerations are in the same frame; dR is used to transform accelerations.