Underwater glider is an emerging platform to explore the ocean with remarkably long operational endurance up to several months. Underwater glider navigation systems have significant limitations, on the other hand, in keeping the navigation error small. There is no reference coordinates information for position estimation and not enough immediate orientation reference for attitude estimation under the sea. Moreover, external disturbances including the sea currents make the navigation error increase further. In order to reduce the navigation error, we exploit a priori knowledge on the average current over the operation area. The performance and the robustness of the proposed algorithm are demonstrated using an experimental data obtained by Korea Institute of Ocean Science & Technology. The algorithm can be used to reduce the navigation error for one glider and also for multiple gliders by fusing the estimated errors. It can be also directly used to predict floating object path in order to use the prediction to design a collision avoidance path
