Performance Evaluation of Tightly-coupled PPP/Rotational IMU Integrated Navigation in Remote Marine Surveying Application
Hao Xiong, Yingwei Zhao, XingShu Wang,Dongkai Dai, College of Optoelectronic Science and Engineering, National University of Defense Technology, China
For satellite monitoring and control, shipborne bathymetry or other surveying application in the remote sea, the position, attitude with high accuracy is needed. Precise point positioning (PPP) technique can achieve similar positioning accuracy as differential GNSS technique without aiding from base stations. This property makes PPP technique suitable for the applications when base stations are unavailable such as remote marine surveying and so on. The main drawback of PPP technique is long convergence time, and frequent reinitialization in challenged environments especially when poor satellite visibility or GPS signal outage happens. By integrating PPP with IMU, IMU can improve PPP performance in challenged environments due to its high short term positioning accuracy, while PPP can estimate inertial sensors’ errors through navigation Kalman filter.
This paper investigates the performance of PPP/IMU tightly-coupled integration in remote marine surveying applications. The structure of PPP/IMU tightly-coupled integration system is introduced at first. A single-rotation IMU composed of three high-quality ring laser gyroscopes (RLG) is used in the remote marine surveying experiment. The rotation modulation technology can and improve the system’s accuracy significantly by eliminate the constant bias of gyroscopes and accelerometer. The receiver used in the study is the SF3050 form NavCom Inc, and the RLG quality is similar to Honeywell GG1320.To simulate the near real-time application, IGS ultra-rapid products are introducing for PPP/IMU tight integration. Since the true position is hard to acquire in remote ocean, two methods are adapted to evaluate the positioning accuracy of PPP/IMU tightly-coupled integration: One is the loosely-coupled integration of NavCom starfireTM PPP positioning result and IMU, and the other is the loosely coupled integration of PPP RTS (Rauch Tung Striebel) result and IMU, which RTS results is using the IGS final products and 30s clk prouducts.
The results indicate that PPP/IMU tightly-coupled integration can achieve better than 10cm horizontal and 20cm vertical positioning accuracy, while the yaw angle estimation error is smaller than 5 arcseconds. Simulated signal outages show that PPP/INS can reach dm-level positioning accuracy even during 100s breaks and the reinitialization time is also greatly reduced, which makes it applicable in remote marine surveying when both high positioning accuracy and yaw angle accuracy are required.