Interesting. I need to look over this compensation for drift then. However, Im still not sure why one cant get acceleration on the Z axis (Im British though, so Z axis means depth to me but in this case, I believe we mean yaw). There is a yaw gyro indeed but it is claimed there is a yaw accelerometer as well. Why is it there if it can't be used? It seems confusing. Clearly I must be missing something.