New time-differenced carrier phase approach to GNSS/INS integration

The accuracy of navigation information is essential for modern transport systems. Such information includes position, velocity and attitude. Because of the physical characteristics of the operational environments, integration of GNSS with inertial measurement units (IMU) is commonly used. However, conventional integrated algorithms suffer from low-quality GNSS measurements due to either inaccurate pseudoranges or difficulty of ambiguity resolution when using carrier phase measurements in urban environments. We propose a Time-Difference-Carrier-Phase (TDCP) derivation controlled GNSS/IMU integration scheme. The proposed algorithm enables a TDCP-based control vector construction, including relative position, velocity, heading and pitch, which makes it possible to obtain accurate changes in position, namely delta position, altitude and velocity estimations. These estimated changes are then used to feed a loosely coupled GNSS/IMU integration system. Real-world test results show that the proposed integrated navigation scheme is superior to the conventional algorithm, with accuracy improvements of more than 38% in 3D positioning, 30% in 3D velocity, 35% in roll, 44% in pitch and 39% in heading.