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    Effect of satellite attitude quaternions on BeiDou precise point positioning during the eclipse season
    LIU Tianjun, CHEN Qusen, JIANG Weiping, CHEN Hua, XIA Fengyu, FAN Caoming
    Acta Geodaetica et Cartographica Sinica    2023, 52 (4): 550-558.   DOI: 10.11947/j.AGCS.2023.20220245
    Abstract303)   HTML30)    PDF(pc) (8413KB)(250)       Save
    In order to obtain high-precision positioning, precise point positioning (PPP) user side should keep the the consistent satellite attitude model with analysis centers. Based on the satellite attitude quaternions products provided by the Wuhan university analysis centers (WUM), we introduce the yaw angle computation method that uses satellite attitude quaternions. When the BDS-2/BDS-3 satellite is at a low sun elevation angle, the satellite attitude model strategy of WUM is analyzed. By using the open-source positioning software GAMP, the BDS-2/BDS-3 PPP solutions are also investigated with different satellite attitude strategies. During the deep eclipse season, the results demonstrate that the differences between nominal and quaternion yaw angles can reach 360°, which can cause the decimeter-level biases in the phase wind-up and antenna phase center offset correction. In this period, compared with the nominal attitude, the positioning accuracy of PPP solutions with satellite attitude quaternions can be improved approximately 32%, 29% and 38% in the earth (E), north (N) and up (U) components, respectively. Furthermore, the positioning accuracy of PPP solutions with satellite attitude quaternions can be improved approximately 29%,25% and 28%in the E, N and U components, respectively, when compared to that of the deleting the eclipsing satellite strategy(deleting satellite at the farthest and closest point of the orbit). The inconsistent attitude models would reduce the reliability of PPP positioning results, so the satellite attitude quaternions that provided from the analysis centers should be used for phase wind-up and antenna phase center offset correction in the PPP user side.
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    Robust GNSS/SINS positioning based on the SE 2(3)-EKF framework
    LI Xin, MENG Shuolin, HUANG Guanwen, ZHANG Qin, LI Hanxu
    Acta Geodaetica et Cartographica Sinica    2023, 52 (10): 1640-1649.   DOI: 10.11947/j.AGCS.2023.20220526
    Abstract233)   HTML23)    PDF(pc) (6055KB)(196)       Save
    For GNSS/SINS integrated navigation, the large errors, such as attitude misalignment angle, will cause the inconsistent coordinates definition of state error and large linearization error, thus the performance of traditional filtering and positioning is reduced, especially in the complex GNSS observation environment. In this paper, the attitude, velocity, and position states are reconstructed as a special SE 2(3) group element, considering the bias of gyro and accelerometer, a group-vector mixed error model is formed, and then one GNSS/SINS robust filtering algorithm (RLIEKF) based on left invariant measurement is studied. The superiority of the proposed method is validated via the vehicle integrated navigation experiment with large misalignment angle error and GNSS outliers in urban environment. The experimental results show that, compared with traditional EKF method, the attitude angle error is considered in time update and GNSS measurement update of the proposed RLIEKF, thus it has a fast convergence speed under different large misalignment angles, without complicated and long-time attitude alignment steps, which can better deal with the problem such the interrupt GNSS signal during a short time. Because the accuracy of innovation is significantly improved, thus it is more robust to complex observation environment, and with a fast computational efficiency, therefore it has excellent engineering practical value.
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    Monitoring global coastline changes over 1987—2016 using Landsat data
    XU Nan
    Acta Geodaetica et Cartographica Sinica    2023, 52 (4): 691-691.   DOI: 10.11947/j.AGCS.2023.20210481
    Abstract200)   HTML18)    PDF(pc) (781KB)(187)       Save
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