Tightly Coupled NavIC and Low-Cost Sensors for Ground Vehicle Navigation

The demand for navigation devices for ground vehicles has been increasing significantly. The presently available Global Navigation Satellite Systems (GNSS) receivers cannot meet the required navigation performance for the ground navigation systems in urban and forest areas due to signal obstructions. Further, with few currently available Navigation with Indian Constellation (NavIC) satellites, computation of navigation solution only with NavIC may not be possible several times. Many researchers propose integrating GNSS and micro-electromechanical systems (MEMS) inertial measurement unit (IMU) for reliable and robust navigation, at low cost for ground vehicles. Therefore, this study implements the tightly coupled integration (TCI) of NavIC with a low-cost MEMS IMU for ground vehicles. Further, quality NavIC measurements based on C/N0 and elevation angle are chosen to improve the accuracy and robustness. Later, barometer-augmented TCI (ATCI) is developed to improve vertical accuracy and applied nonholonomic constraints to improve the standalone MEMS inertial navigation system (INS) performance during an outage. Experiments are conducted on real data collected using NavIC/GPS and MEMS IMU devices for urban environments. The results of TCI and ATCI algorithms are analyzed and compared for six modes: 1) TCI NavIC/INS; 2) TCI GPS/INS; 3) TCI NavIC/GPS/INS; 4) ATCI NavIC/INS; 5) ATCI GPS/INS; and 6) ATCI NavIC/GPS/INS with and without outages. The results show that the ATCI NavIC/INS with three satellites outperforms TCI NavIC/INS with four satellites, decreasing the horizontal root-mean-square (rms) error from 4.52 to 4.38 m and the vertical rms error from 2.6 to 1.39 m. The algorithms and analysis presented in this article will be useful in developing low-cost navigation solution for ground vehicles.