NED to ENU conversion of IMU Message Type

[sbillin]

NED to ENU conversion of IMU Message Type

[sbillin]

Ok, so I think I understand this now. The linear acceleration and angular velocity terms are changed because not only is the world frame changed from NED to ENU but the local sensor frame is being changed as well from {x-forward, y-right, z-down} to {x-right, y-forward, z-up}. The reason for this is because now the new sensor frame will align with the new ENU world frame at the same right-side-up position as before. Without the change in sensor frame, the IMU would have to be upside-down and yawed 90 degrees for its sensor frame to align with the new ENU world frame, which is not a problem mathematically but is less natural.