Sensors Sensors 1424-8220 SENSC9 3 2015 15 3 Tightly Coupled Integration of Ionosphere-Constrained Precise Point Positioning and Inertial Navigation Systems Zhouzheng Gao School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuhan 430079, China German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam 14473, Germany Hongping Zhang GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuhan 430079, China Maorong Ge German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam 14473, Germany Xiaoji Niu GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuhan 430079, China Wenbin Shen School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China Jens Wickert German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam 14473, Germany http://orcid.org/0000-0002-7379-5276 Harald Schuh German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam 14473, Germany

The continuity and reliability of precise GNSS positioning can be seriously limited by severe user observation environments. The Inertial Navigation System (INS) can overcome such drawbacks, but its performance is clearly restricted by INS sensor errors over time. Accordingly, the tightly coupled integration of GPS and INS can overcome the disadvantages of each individual system and together form a new navigation system with a higher accuracy, reliability and availability. Recently, ionosphere-constrained (IC) precise point positioning (PPP) utilizing raw GPS observations was proven able to improve both the convergence and positioning accuracy of the conventional PPP using ionosphere-free combined observations (LC-PPP). In this paper, a new mode of tightly coupled integration, in which the IC-PPP instead of LC-PPP is employed, is implemented to further improve the performance of the coupled system. We present the detailed mathematical model and the related algorithm of the new integration of IC-PPP and INS. To evaluate the performance of the new tightly coupled integration, data of both airborne and vehicle experiments with a geodetic GPS receiver and tactical grade inertial measurement unit are processed and the results are analyzed. The statistics show that the new approach can further improve the positioning accuracy compared with both IC-PPP and the tightly coupled integration of the conventional PPP and INS.

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