  The above-mentioned work [1] in IEEE-TR'08 presented an extended Kalman
filter for calibrating the misalignment between a camera and an IMU. As one of
the main contributions, the locally weakly observable analysis was carried out
using Lie derivatives. The seminal paper [1] is undoubtedly the cornerstone of
current observability work in SLAM and a number of real SLAM systems have been
developed on the observability result of this paper, such as [2, 3]. However,
the main observability result of this paper [1] is founded on an incorrect
proof and actually cannot be acquired using the local observability technique
therein, a fact that is apparently not noticed by the SLAM community over a
number of years.
