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Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press 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: In order to effectively filter out complex noise components in GNSS coordinate time series and extract effective signals, we construct a denoising method based on parameter-optimized variational modal decomposition (VMD). Methods: First, the combination of permutation entropy and mutual information is used as fitness function, and the optimal parameter combination of the mode decomposition number K and the quadratic penalty factor α of VMD is obtained by using grey wolf optimization algorithm (GWO). Then the GNSS coordinate time series is decomposed into K eigen mode function components by VMD. Finally, the sample entropy is used to determine the effective modal component, which is reconstructed as an effective signal, so as to realize the effective separation of signal and noise.The GWO-VMD method is compared and analyzed with the empirical mode decomposition (EMD), wavelet denoising (WD) and IVMD methods by using the simulated signal and the measured data from 20 reference stations of the crustal movement observation network of China for experiments. Results: The simulated signal experiments show that the three denoising evaluation indexes of root mean square error,correlation coefficient and signal-to-noise ratio of GWO-VMD denoising signal are better than EMD, WD and IVMD methods. The experiments on the measured data show that the GWO-VMD method can reduce the amplitude of noise significantly. In terms of the velocity uncertainty of the reference station, the overall GWO-VMD method reduces the velocity uncertainty better than the EMD, WD and IVMD methods. Conclusions: The GWOVMD method can more effectively remove the noise from GNSS coordinate time series and better preserve the original characteristics of the signal, which can provide reliable data for subsequent analysis and processing. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics 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.)

Urban ecological environmental quality monitoring is a necessary factor to achieve urban green development. Remote sensing technology is widely used in urban ecological environment quality evaluation with its advantages of large monitoring scope and real-time transmission. In order to objectively reflect the quality of the urban ecological environment, remote sensing based ecological index (RSEI) could be used for evaluation. However, the RSEI has the problem of the low contribution rate of the first principal component, which makes the evaluation results less accurate. Therefore, improved remote sensing ecological index ( IRSEI) was used to improve the accuracy of the model in evaluating the ecological environment quality, which replaced normalized difference vegetation index (NDVI) with universal normalized vegetation index(UNVI). The Landsat remote sensing image of Nanchang City 2003—2021 was processed to obtain the distribution and change of the quality of ecological environment. The results show that the contribution rate of the first principal component of IRSEI was 3. 6% higher than that of RSEI, and the average correlation degree of humidity, greenness, dryness and heat in each year was 7. 2% higher than that of RSEI. From 2003 to 2021, the overall mean of IRSEI in Nanchang did not change significantly. The areas with high ecological quality were mainly distributed in Poyang Lake region, Meiling and Anyi counties, while the areas with low ecological quality were mainly distributed in the central city and Liuhu Town in the southwest. It is concluded that the overall ecological environment quality of Nanchang City showed a downward trend and then continued to rise from 2003 to 2021. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics 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: In order to solve the problem of the accuracy and efficiency of the noise component of the global navigation satellite system (GNSS) coordinate time series, combined with the equivalent conditional adjustment model and the minimum norm quadratic unbiased estimation method, an equivalent conditional closure error minimum norm component estimation method is proposed. Methods: First, we use the equivalent conditional closure error to construct the quadratic variance estimation formula, and combine the conditions of invariance, unbiasedness, and minimum norm criterion to derive the minimum norm estimation formula of the variance-covariance component based on the equivalent conditional closure error. Second, least-squares variance component estimation(LS-VCE) method, minimum norm quadratic unbiased estimate (MINQUE) method and our proposed method are used to calculate the noise amplitude of simulated time series and North American GNSS station coordinate time series respectively, and the calculation time of our method and LS-VCE method are calculated. Results and Conclusions: The estima tion effect of the MINQUE method is consistent, and its calculation time decreases over 70% of the LS)VCE method, which verifies the correctness and the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press 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 Science Technology & Engineering is the property of Chinese Society of Technology Economics 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 Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics 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 Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics 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 Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics 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 Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics 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.)

Quality control is described by internal and external reliability according to the Delft philosophy. Internal reliability describes the ability to find biases in observational data and is represented accordingly by the minimal detectable bias (MDB). The MDBs formulas of four popular outliers detection methods include data snooping, quasi-accurate detection of gross errors(QUAD), partly least squares (PLS) and the method of simultaneous locating and evaluating multiple gross errors(LEGE) are derived with the given significance level α0 and given power of test β0. The numerical example reveals that MDBs are same value when the observations have the same weight. If the clean data are not equally weighted, the MDBs of data snooping are equal to that of QUAD and PLS,but all are slightly smaller than the MDBs of LEGE. If the clean data are correlated observations, the MDBs of QUAD are equal to that of PLS, but both are larger than that of data snooping and smaller than that of LEGE. [ABSTRACT FROM AUTHOR]