Recently, integrated navigation systems utilizing multiple sensors have been actively studied to obtain a stable and accurate navigation solution in GPS-denied environments where the signal reception of the Global Positioning System (GPS) is difficult. In these environments, augmentation by a low-cost Micro Electro Mechanical System (MEMS) Inertial Measurement Unit (IMU) alone not sufficiently helpful in maintaining navigation accuracy due to its low performance. To mitigate this problem, we propose a tightly-coupled GPS/INS/ultrasonic-speedometer/barometric-altimeter navigation system to obtain more stable and accurate navigation solutions in GPS-denied environments. To evaluate the performance of the proposed system, an experiment was carried out by driving a test vehicle and gathering actual measurements. The experiment results were compared with Real-Time Kinematic (RTK) GPS.

Keywords: GPS-denied environment, GPS/INS/sensors, low-cost sensor, tightly-coupled navigation system