Dual-mode GNSS gyrocompass using primary satellite measurements

The paper presents the results of developing an all-latitude tightly-coupled inertial/satellite system, when solving both orientation and navigation problems, under the conditions of limited visibility of navigation satellites (NS). The processed bench test data are presented for the breadboard model of a dual-mode GNSS gyrocompass, with the antenna baseline being about a wavelength, which comprises two GNSS receivers integrated with inertial measurement unit (IMU) on low-accuracy fiber-optic gyros (FOG). Specific feature of GNSS compass consists in arranging the IMU and antenna module on the same rotating platform, setting a timescale of satellite receivers from the same external reference generator, all-latitude high-accuracy determination of heading angle in the presence of at least one visible NS and with its absence, in gyrocompassing mode. The GNSS gyrocompass uses an alternative algorithm of heading determination by phase measurements with simultaneous observation of only one NS, providing 1 deg accuracy. Kinematic parameters of vehicle motion are received using both GPS and GLONASS NS. In GNSS compass the difference phase measurements are generated at the level of the first phase differences. Velocity, position, and phase difference measurements are processed using generalized Kalman filter.