A Virtual Vertical Reference Concept for GNSS/INS Applications at the Sea Surface

Inertial navigation systems (INS) can be used to obtain estimates of the position, velocity and attitude, in a dead-reckoning fashion, for marine vessels. To combat drift, aiding reference systems such as global navigation satellite systems are utilized. However, satellite based positioning systems typically provide less accurate measurements of the vertical position. This paper presents an alternative vertical aiding by introducing a virtual vertical reference concept with respect to uncoupled and loosely coupled GNSS/INS integration, which improves the accuracy of nonlinear observers significantly when applied to strapdown inertial navigation. The estimation performance obtained with the virtual vertical reference concept is compared with the performance obtained with standalone GNSS, and differential corrected GNSS through simulations.