Various aiding sensors can be integrated with the inertial navigation system (INS) to reduce its error growth when the vehicle is operating in GNSS denied environments.This paper developed a method to use the vanishing point from vertical line observations ofbuilding blocks in order to further improvepoint-based visual-inertial navigation system (VINS) for land vehicle applications.First,we presented the formulations oftightly coupled point-based VINS based on the Multi- State Constraint Kalman Filter (MSCKF) in the local-level frame.Second,we developed the relationship between the INS roll angle andvanishing point coordinates from vertical line observations.The roll angle measurement model is formulated.Finally,loosely coupled vertical line aiding module is added to the existing- VINS,and the integration scheme is presented.Real world experimentsdemonstrated the validity of the mixed VINS method and the improved accuracy of the attitude and position estimation whencompared with the solution without vertical linevanishing pointaiding.