In this paper,an improved weighted least squares(WLS),together with autoregressive(AR) model,is proposed to improve prediction accuracy of earth rotation parameters(ERP).Four weighting schemes are developed and the optimal power e for determination of the weight elements is studied.The results show that the improved WLS-AR model can improve the ERP prediction accuracy effectively,and for different prediction intervals of ERP,different weight scheme should be chosen.
A new velocity determination algorithm with combination of remove and restore method,outliers detection method and Chebyshev fitting method with redundant observations is proposed.An optimal selection of number of sampling points is given.The result shows that,when the number of sampling points is 19,the three-dimension (3D) interpolation precision of velocity is superior to 0.1 mm/s,which is above 3 times better than that of Chebyshev fitting method with redundant observations and far better than those of the conventional interpolation methods.
The main principle and mathematical model of GOCE kinematic orbit adjustment for Earth gravity field model(EGM)validation and accelerometer calibration are presented.Based on 60 days GOCE kinematic orbits with 1-2 cm accuracy and accelerometer data from 2009-11-02 to 2009-12-31,the RMS-of-fit(ROF)of them using EGM2008,EIGEN-5C,ITGGRACE2010S and GOCO01S up to 120,150 and 180 degree and order(d/o)are evaluated and compared.The scale factors and biases of GOCE accelerometer data are calibrated and the energy balance method(EBM)is performed to test the accuracy of accelerometer calibration.The results show that GOCE orbits are also sensitive to EGM from 120 to 150 d/o.The ROFs of EGMs with 150 and 180 d/o are obviously better than those of EGMs with 120 d/o.The ROFs of GOCO01S and ITG-GRACE2010S are almost the same up to 120 and 150 d/o,which are about 3.3 cm and 1.8 cm,respectively.They are far better than those of EGM2008 and EIGEN-5C with the same d/o.The ROF of GOCO01S with 180 d/o is about 1.6 cm,which is the best one among those EGMs.The accelerometer calibration accuracies(ACAs)of ITG-GRACE2010S and GOCO01S are obviously higher that those of EGM2008 and EIGEN-5C.The ACA of GOCO01S with 180 d/o is far higher than that of EGMs with 120 d/o,and a little higher than that of ITG-GRACE2010S with 150 d/o.It is suggested that the newest released EGM such as GOCO01S or GOCO02S till at least 150 d/o should be chosen in GOCE precise orbit determination(POD)and accelerometer calibration.
Satellite gravity data fusion with multi-type and huge-amount is one of the hot topics in physical geodesy.After a brief review of dynamic approach,the CHAMP-only and GRACE-only gravity fields by using HL-SST and LL-SST data from 2003 to 2009 are recovered respectively.An combination strategy of CHAMP and GRACE data by using Helmert variance component estimation(VCE) is proposed based on normal equation level fusion.Three gravity field models with 150° and order by CHAMP-only data,GRACE-only data and combining CHAMP and GRACE data from 2003 to 2009 are recovered.The comparisons between our recovered models and those latest released models were performed.The external accuracy validations using marine gravity anomalies from DTU13 products and height anomalies from GPS/leveling data are also conducted in this paper.The results show that long-term CHAMP data do contribute to the accuracy improvement of gravity field solution.The accuracy of the combined model using CHAMP and GRACE data is better than those of the individuals and comparative to the models published by international groups.
