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In a GNSS/INS integrated system,the GNSS outputs,such as position and velocity,are used to estimate the INS navigation errors and inertial sensor errors and the inertial solutions are used to bridge the GNSS outages for which a good quality IMU is needed.Since MEMS IMU outputs are corrupted by significant sensor errors,the navigation errors will accumulate quickly which degrade the navigation solution over a short time period in the presence of GNSS outages.The rotary INS technique has been proposed to reduce the MEMS-based INS navigation errors recently.A rotary INS is an inertial navigator in which the IMU is installed on a rotation platform.By modulating the significant inertial sensor errors through proper IMU rotations,the accumulation of navigation errors can be effectively mitigated without a need for external aiding.Based on the previous work on MEMS-based rotary INS,this paper proposed an integrated system of GNSS and rotary INS.Given the ability of a rotary INS to extend autonomous navigation,the integrated system can significantly improve the navigation performance to bridge GNSS outages under GNSS-challenging environments,such as vehicles travelling through tunnels.Based on a single-axis rotation table,roadkinematic tests are conducted to evaluate the performance of the proposed system using two different MEMS IMUs (MTi-G fromXsens and NAV440 from Moog Crossbow).The results indicate that the IMU rotation can reduce the horizontal position errors by about 2 times for the system with MTi-G and about 3 times for the system with NAV440 during the period of GNSS outages.