“…On the other hand, the images are collected by the stereo camera; after performing the feature detection and initialization which will be discussed in the next subsection, the error-state and measurement equations can be established by (22), (23), (24), (25), (26), (27), (28), (29), (30), (31), (32), (33), (34), (35), (36), (37), and (38) with the IMU measurement and the update result of the inertial navigation. In the last step, the EKF estimator is executed by (39) and (40). In addition, the covariance matrix of the EKF should be augmented when new point or line features are observed.…”