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. 2015 Apr 14;15(4):8685-711.
doi: 10.3390/s150408685.

Performance analysis on carrier phase-based tightly-coupled GPS/BDS/INS integration in GNSS degraded and denied environments

Houzeng Han  1 , Jian Wang  2 , Jinling Wang  3 , Xinglong Tan  4
Affiliations

Performance analysis on carrier phase-based tightly-coupled GPS/BDS/INS integration in GNSS degraded and denied environments

Houzeng Han et al. Sensors (Basel). .

Abstract

The integration of Global Navigation Satellite Systems (GNSS) carrier phases with Inertial Navigation System (INS) measurements is essential to provide accurate and continuous position, velocity and attitude information, however it is necessary to fix ambiguities rapidly and reliably to obtain high accuracy navigation solutions. In this paper, we present the notion of combining the Global Positioning System (GPS), the BeiDou Navigation Satellite System (BDS) and low-cost micro-electro-mechanical sensors (MEMS) inertial systems for reliable navigation. An adaptive multipath factor-based tightly-coupled (TC) GPS/BDS/INS integration algorithm is presented and the overall performance of the integrated system is illustrated. A twenty seven states TC GPS/BDS/INS model is adopted with an extended Kalman filter (EKF), which is carried out by directly fusing ambiguity fixed double-difference (DD) carrier phase measurements with the INS predicted pseudoranges to estimate the error states. The INS-aided integer ambiguity resolution (AR) strategy is developed by using a dynamic model, a two-step estimation procedure is applied with adaptively estimated covariance matrix to further improve the AR performance. A field vehicular test was carried out to demonstrate the positioning performance of the combined system. The results show the TC GPS/BDS/INS system significantly improves the single-epoch AR reliability as compared to that of GPS/BDS-only or single satellite navigation system integrated strategy, especially for high cut-off elevations. The AR performance is also significantly improved for the combined system with adaptive covariance matrix in the presence of low elevation multipath related to the GNSS-only case. A total of fifteen simulated outage tests also show that the time to relock of the GPS/BDS signals is shortened, which improves the system availability. The results also indicate that TC integration system achieves a few centimeters accuracy in positioning based on the comparison analysis and covariance analysis, even in harsh environments (e.g., in urban canyons), thus we can see the advantage of positioning at high cut-off elevations that the combined GPS/BDS brings.

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Figures

Figure 1
Figure 1
Implementation of the carrier phased-based tightly coupled GPS/BDS/INS integration.
Figure 2
Figure 2
Performance analysis of the GPS/BDS/INS combined system in GNSS degraded and denied environments.
Figure 3
Figure 3
Testing platform.
Figure 4
Figure 4
Field test trajectory (vehicle operated under foliage in the area marked by a red circle).
Figure 5
Figure 5
Sky plots of GPS/BeiDou satellites during the field test.
Figure 6
Figure 6
Satellites visibility and PDOP during the field test (15° cut-off elevation).
Figure 7
Figure 7
Impact of system configuration on ADOP (INS position STD 0.1 m, 15° cut-off elevation).
Figure 8
Figure 8
(a) Effect of pseudorange accuracy on ADOP; (b) Effect of INS position accuracy on ADOP.
Figure 9
Figure 9
(a) Estimated accelerometer biases and RMS; (b) Estimated accelerometer scale factors and RMS.
Figure 10
Figure 10
(a) Estimated gyro biases and RMS; (b) Estimated gyro scale factors and RMS.
Figure 11
Figure 11
Ratio values of instantaneous AR for different system configurations (20° cut-off elevation).
Figure 12
Figure 12
Ground track of test vehicle with simulated GNSS outages.
Figure 13
Figure 13
Average of the maximum position error vs. outage duration for different system configurations.
Figure 14
Figure 14
Time to fix ambiguity after different outage durations for different system configurations.
Figure 15
Figure 15
RMS of position difference vs. cut-off elevation angle for different system configurations.
Figure 16
Figure 16
Position differences between GPS/BDS/INS integration solution and GPS/BDS solution (20° cut-off elevation).
Figure 17
Figure 17
RMS of the estimated position errors.
Figure 18
Figure 18
RMS of the estimated velocity errors.
Figure 19
Figure 19
RMS of the estimated attitude errors.
Figure 20
Figure 20
(a) RMS values of GPS DD residual; (b) RMS values of BDS DD residual.
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