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Objectives The critical problem to be solved in the construction of a high-precision seafloor control network is to reduce the influence of systematic errors on the coordinate accuracy of seafloor control points during acoustic positioning.Methods First, we analyze two positioning models: Non-difference and difference between epochs. Second, due to the change of sound velocity in seawater is affected by the long period term error and the short period term error, the system error caused by the shift in sound velocity in the measurement also has the characteristics of periodic change.Results and Conclusions Based on this premise, a symmetric epoch differential positioning model was constructed. The results of simulation analysis and measured data analysis show that when the observation duration is an even multiple of the system error variation period, the symmetric differential positioning model can effectively reduce the influence of the system error on the positioning results. Still, when the observation duration is not an even multiple of the system error variation period, the model is no longer applicable. [ABSTRACT FROM AUTHOR]

Objectives: The measurement of three-dimensional absolute coordinates of high-precision seafloor control points is a key step in the construction of seafloor geodetic control network. The underwater positioning method based on the navigation of the survey ships is an important method to solve this problem. However, the measuring routes are spatially limited, which result in less accurate solutions for the vertical coordinates of the control points. To solve this problem, we improve the coordinate calculation method, and use the vertical solution correction value to correct the reference depth information during the iterative process, which improved the accuracy of the slant distance calculation, so that the purpose of improving the accuracy of the vertical solution is achieved. Methods: First, the concept of the position line with the same propagation time is introduced. Based on this concept, the influence of the error of reference depth on the calculation of slant range is analyzed. Then the model convergence process of control point positioning under different error relationship curves is analyzed. The position relationship between the reference depth and the real water depth is determined according to the positive or negative of coordinate correction value. Finally, the vertical coordinate correction value is used to correct the reference depth information, so that the accuracy of vertical solution is improved. Results: The experimental results show that: (1) When the gradient value of the errors relation curve is not zero and there is no error in the sound velocity profile, the traditional method is affected by the reference depth error, so that the error of the vertical solution of the control point coordinate is an order of magnitude higher than that of the horizontal solution. While the new method is almost unaffected. (2) The sound velocity error has little effect on the horizontal solution and a large effect on the vertical solution, and increases with depth. (3) The reference depth error is coupled with the sound velocity error, which further increases the vertical solution error. The new method can reduce the coupling effect. Conclusions: When the gradient value of errors relation curve is zero, the reference depth error causes little change on the positioning result. When the gradient value of errors relation curve is not zero, the reference depth error increases the vertical solution error. The new method can reduce the impact of the reference depth error on the positioning of seafloor control point, and weaken the coupling effect of the sound velocity error and the reference depth error. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Earth Science (1001-8166) is the property of Advances in Earth Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objectives: A terrestrial reference system (TRS) is a spatial reference system corotating with the Earth in its diurnal motion in space. A terrestrial reference frame (TRF) is defined as the realization of a TRS, through the realization of its origin, orientation axes and scale, and their time evolution. The TRF is the basis of all surveying and mapping activities and earth science research. Usually, its realization is achieved by a set of physical points with precisely determined coordinates in a specific coordinate system. Methods:The instantaneous positions obtained from different epoch observations are with respect to different reference frames. It is necessary to accumulate the instantaneous positions to form a stable long⁃term reference frame. Taking the instantaneous positions obtained from different epoch observations as input, a fusion model for the long⁃term solutions to a TRF is designed. The function model for the long⁃term solutions is deduced in detail considering the coordinate transformation model and the time⁃varying model of station coordinates. The rank deficiency is solved by applying internal constraints to the Helmert transformation parameters.Results:The daily solutions spanning from 2010⁃08−2014⁃12 from the second reprocessing of International Global Navigation Satellite System Service are used for calculation, and the results are compared with that of the international terrestrial reference frame 2014 (ITRF2014). The results show that for daily solutions the standard deviation is 3.45 mm, 4.04 mm, and 2.84 mm for X, Y and Z directions, respectively, and the weighted root mean square is better than 3 mm for all three directions. In terms of velocity, the accuracy is 1.53 mm/a, 1.46 mm/a, and 1.21 mm/a for X, Y and Z directions, respectively. Conclusions: The derived TRF using the fusion model is consistent with ITRF2014, and the results validate the correctness and reliability of our fusion model, which can provide a theoretical basis for the establishment of the reference frame. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The ERP (Earth rotation parameters) obtained by different technologies and different analysis centers are often different. In order to provide unified ERP for users, it is often necessary to fuse the ERP by using a special method. In this paper, an additional boundary constraints and internal constraints fusion model based on the ERP results of multi-analysis center is proposed. Firstly, all the analysis center results are converted to the same time by using the parameter transformation model and the boundary constraints are applied to the same characteristic points on the boundary point of the adjacent observation period. Then the inner constraints of the transformation parameters are applied to the long-term solutions of the analysis centers, and the fusion solutions of the ERP are obtained. Using SINEX (solution independemt exchange format) files from seven GNSS (Global Navigation Satellite System) analysis centers of six years from 2005 to 2011, their results are integrated and analyzed. Compared with the results of IERS C04 (International Earth Rotation and Reference Systems Service Combined 04), the results of the fusion method proposed in this paper have been significantly improved. [ABSTRACT FROM AUTHOR]

Navigation users will significantly benefit from BDS and GPS positioning fusion in terms of availability, accuracy and reliability. However, for single point positioning, systematic biases between multi-GNSS systems cannot be eliminated completely, thus the accuracy of positioning and navigation is not always improved with the un-difference measurements of multi-GNSS systems. In this paper, an integrated BDS/GPS positioning model with unknown systematic parameters that compen­sates for systematic bias is proposed. Furthermore, a Bayesian estimation of fusion positioning model is specifically investigated in which the priori information of the additional parameters is taken into ac­count. Real data collected from different areas with different types of receivers are used to verify those new algorithms. The results show that (a) receiver-dependent inter-system biases are quite evident, while the size of the system bias varies with the receiver type; (b) the precision of fusion positioning is improved significantly by introducing additional parameters into the functional model; and ( c) Bayesian estimation of fusion positioning model can still obtain ideal position solution when the num­ber of visible satellites is not enough. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)