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Chen Q.,Tongji University | Chen Q.,Hong Kong Polytechnic University | Shen Y.,Tongji University | Zhang X.,Guangdong University of Technology | And 2 more authors.
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2016

To recover the highly accurate static earth's gravity field by using GRACE satellite data is one of the hot topics in geodesy. Since linearization errors of dynamic approach quickly increase when extending satellite arc length, we established a modified dynamic approach for processing GRACE orbit and range-rate measurements in this paper, which treated orbit observations of the twin GRACE satellites as approximate values for linearization. Using the GRACE data spanning the period Jan. 2003 to Dec. 2010, containing satellite attitudes, orbits, range-rate, and non-conservative forces, we developed two global static gravity field models. One is the unconstrained solution called Tongji-Dyn01s complete to degree and order 180; the other one is the Tongji-Dyn01k model computed by using Kaula constraint. The comparisons between our models and those latest GRACE-only models (including the AIUB-GRACE03, the GGM05S, the ITSG-Grace2014k and the Tongji-GRACE01) published by different international groups, and the external validations with marine gravity anomalies from DTU13 product and height anomalies from GPS/levelling data, were performed in this study. The results demonstrate that the Tongji-Dyn01s has the same accuracy level with those of the latest GRACE-only models, while the Tongji-Dyn01k model is closer to the EIGEN6C2 than the other GRACE-only models as a whole. © 2016, Surveying and Mapping Press. All right reserved.

Ma X.,Tongji University | Shen Y.,Center for Spatial Information Science and Sustainable Development
Lecture Notes in Electrical Engineering | Year: 2013

In this paper, we carried out GPS and BeiDou relative positioning with our developed software using the real data collected in Beijing and Shanghai, respectively, and assessed the accuracy of single epoch baseline solution of the two systems. For short baseline, the relative positioning accuracies of the two systems are basically the same, and the vertical accuracy of the baseline of BeiDou is better than that of GPS. The solved time series errors mainly contain the multipath error and random noise. We used wavelet filtering to extract multipath error according to the frequency characteristics of the random noise and multipath errors. Subsequently, the analysis of GPS and BeiDou multipath was carried out to find the differences between them. Finally, sidereal filtering based on the orbit characteristics of BeiDou was used to eliminate multipath error and improve the relative positioning accuracy. The results showed that the accuracy of relative positioning for short baselines can improve up to 10 % after the multipath error is filtered out. © 2013 Springer-Verlag Berlin Heidelberg.

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