Accuracy Analysis of GNSS/INS Deeply-Coupled Receiver for Strong Earthquake Motion

Abstract

With the development of high-frequency GNSS receivers and precision positioning technology, GNSS has been one of the main observation means to obtain high precision crustal deformation information in seismic monitoring. However, the measurement accuracy of carrier phase of GNSS receiver is obviously decreased under the motion condition, which affects the performance of GNSS. The accelerograph and the GNSS are highly complementary, and the combination of the two has been extensively studied in seismic monitoring in recent years. The loose couple and the tight-couple are integrated at the data level, which has no help to improve GNSS carrier phase accuracy. GNSS/INS deep integration implements the signal level aiding of GNSS receiver by INS (Inertial Navigation System), which can improve the carrier phase accuracy. In this paper, we focus on analyzing carrier phase accuracy of the GNSS/INS deeply-coupled receiver under strong earthquake conditions. First, we discuss the spectrum characteristics of strong earthquake signals, and analyze the tracking error of PLL (Phase-locked Loops) before and after IMU (Inertial Measurement Unit) aiding under strong earthquake based on the error model. Then, the carrier tracking performance of the loop before and after IMU aiding is tested on our self-developed software deep integration receiver, with strong earthquake motion generated by a GPS/INS hardware signal simulator. The analysis and testing results show that the tracking error of PLL with INS aiding is significantly smaller than traditional PLL. The RMS of phase discriminator error of INS-aided carrier PLL with the optimized bandwidth is smaller than 6° under the 2G single frequency simulation conditions, which is consistent with the analysis.