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APPLICATION OF ANALYTIC HIERARCHY PROCESS TO ASSESSING THE ECOLOGICAL VULNERABILITY OF WETLANDS IN THE JIANGHAN PLAIN

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chinese Geographical Science 2003年第3期13卷 272-276页

作者： WANG Xue-lei, NING Long-mei, HU Wang-bin(institute of geodesy and geophysics, chinese academy of sciences, Wuhan {4., P. R. china) institute of geodesy and geophysics Chinese Academy of Sciences Wuhan P. R. China

Wetlands in the Jianghan Plain are important components of wetland types in lake area in the middle and lower reaches the Changjiang (Yangtze) River and they fulfill many uses and functions related to hydrology, waste assimilation, ecosystem productivity and biodiversity. Owing to natural factors and human activities, especially excessive reclamation from lakes, the shrinking process of the lakes has been accelerated. Wetland ecosystem has shown the characteristics of vulnerability. According to the analysis of wetland ecological function in the Jianghan Plain, this paper presented an index system related to productivity, stability and environmental capacity. By using the method of Analytic Hierarchy Process, we computed the values of the relative weights of the indexes, and evaluated the vulnerability level of the wetland ecosystem by the method of multi-indexes. The case study showed that the fragile extent of wetland ecosystem in the Jianghan Plain is 5.6. This means that the wetland ecosystem in the Jianghan Plain is laid to the state of middle vulnerability. Therefore, the wetland conservation and eco-rehabilitation in the Jianghan Plain should be paid attention to.

关键词： wetland ecological vulnerability AHP the jianghan plain

Optimal carrier-smoothed-code algorithm for dual-frequency GPS data

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Progress in Natural Science:Materials International 2008年第5期18卷 591-594页

作者： Jianfeng Guo a,b, Jikun Ou a, Yunbin Yuan a, Haitao Wang a a Key Laboratory of Geodynamics, institute of geodesy and geophysics, chinese academy of sciences, Wuhan {4., china b institute of Science, Information Engineering University, Zhengzhou 4.0001, china Key Laboratory of Geodynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China institute of Science Information Engineering University Zhengzhou 450001 China

Carrier-smoothed-code (CSC) algorithm is an e ective pseudorange multipath mitigation technique, which can alleviate the compu- tational burden and reduce the communication bandwidth needed for the transmission of GPS observations. This paper presents an improved Hatch lter and addresses the optimal CSC algorithm for dual-frequency GPS data based on the optimal parameter estimation theory. The smoothed observations have the same information content as that of the raw dual-frequency GPS data from which these are derived. Consequently, the optimal CSC algorithm is equivalent to the uncombined algorithm. Theoretical analyses show that the data precision of the optimal CSC algorithm is better than that of Hatch lter and its improved version.

关键词： GPS Carrier-smoothed-code algorithm Hatch lter Time-invariant combinations

Variation properties of ionospheric eclipse factor and ionospheric influence factor

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Progress in Natural Science:Materials International 2005年第6期15卷 573-576页

作者： ZHAO Chunmei 1,2 *, YUAN Yunbin1, OU Jikun1 and CHEN Jinping3(1. institute of geodesy and geophysics, chinese academy of sciences, Wuhan {4., china 2. Graduate School of chinese academy of sciences, Beijing 100039, china 3. Department of Precision Instrument and Mechanology, Tsinghua University, Beijing 100084. china) institute of geodesy and geophysics Chinese Academy of Sciences Wuhan 430077 China Graduate School Chinese Academy of Sciences Beijing 100039 China Department of Precision Instrument and Mechanology Tsinghua University Beijing 100084 China

The concepts and calculation methods of ionospheric eclipse factor (IEF) and ionospheric influence factor (IFF) are further illustrated. The temporal and spacial variation properties of IEF and IFF are studied, which shows that the properties are influenced by the geographic position and season. The possibility of improving the precision of using GPS data to determine ionospheric delay based on the above variation properties is also analysed.

关键词： GPS Ionospheric eclipse factor Ionospheric influence factor

Experimental earth tidal models in considering nearly diurnal free wobble of the Earth's liquid core

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Science Bulletin 2003年第9期48卷 935-940页

作者： SUN Heping, XU Jianqiao & B. Ducarme Key Laboratory of Dynamic geodesy, institute of geodesy and geophysics,{4., Wuhan 4.0077, china Observatoire Royal de Belgique, Av. Circulaire 3, B-1180, Brussels, Belgium Correspondence should be addressed to Sun Heping (e-mail: heping@ ***) Key Laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Observatoire Royal de Belgique Av. Circulaire 3 B-1180 Brussels Belgium

Based on the 28 series of the high precision and high minute sampling tidal gravity observations at 20 stations in Global Geodynamics Project (GGP) network, the resonant parameters of the Earth's nearly diurnal free wobble (including the eigenperiods, resonant strengths and quality factots) are precisely determined. The discrepancy of the eigenperiod between observed and theoretical values is studied, the important conclusion that the real dynamic ellipticity of the liquid core is about 5% larger than the one under the static equilibrium assumption is approved by using our gravity technique. The experimental Earth's tidal gravity models with considering the nearly diurnal free wobble of the Earth's liquid core are constructed in this study. The numerical results show that the difference among three experimental models is less than 0.1%, and the largest discrepancy compared to those widely used nowdays given by Dehant (1999) and Mathews (2001) is only about 0.4.. It can provide with the most recent real

关键词： Earth’s nearly diurnal free wobble global observations of superconducting gravimeters dynamic ellipticity of liquid core experimental earth tidal models.

Source mechanism of strong aftershocks (M_s≥5.6) of the 2008/05/12 Wenchuan earthquake and the implication for seismotectonics

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Science china Earth sciences 2009年第6期52卷 739-753页

Dozens of >M5, hundreds of >M4. and much more >M3 aftershocks occurred after the 2008/05/12 Wenchuan earthquake, which were well recorded by permanent and portable seismic stations. After relocated with P arrival, the >M3 aftershocks show two trends of distribution, with most of the aftershocks located along the north-east strike consistent with Longmenshan fault system, yet there is a north-west trend around the epicenter. It seems that substantially more aftershocks occur in regions with crystalline bedrocks. Then we collected waveform data from National Digital Seismograph Network and regional seismograph network of china, and employed 'Cut and Paste' method to obtain focal mechanisms and depths of the big aftershocks (M≥5.6). While most of those aftershocks show thrust mechanism, there are some strike slip earthquakes in the northern-most end of the rupture. Focal mechanisms show that the events located on the southern part of central Beichuan-Yingxiu Fault (BY) are mainly thrust earthquakes, which is consistent with initial mechanism of the main shock rupture. In the north part the aftershocks along the BY are also dominated by thrust slip, which is quite different from the right slip rupture of the main shock. Around Qingchuan-Pingwu Fault, the focal mechanisms are dominated by right-slip rupture with large depths (~18 km). So we suspected that in the north part the main shock might rupture on two faults: Beichuan Fault and Qingchuan-Pingwu Fault. The complex pattern of aftershock mechanisms argues for presence of a complicated fault system in the Longmenshan area.

关键词： focal mechanism seismotectonics Wenchuan earthquake cut and paste.

Simulation of the Earth' s gravitational field recovery from GRACE using the energy balance approach

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Progress in Natural Science:Materials International 2005年第7期15卷 596-601页

作者： ZHENG Wei, LU Xiaolei, HSU Houtse, SHAO Chenggang, LUO Jun and WANG Nengchao ( Department of Physics, Huazhong University of Science and Technology, Wuhan 4.0074. china institute of geodesy and geophysics,{4., Wuhan 4.0077, china Department of Mathematics, Huazhong University of Science and Technology, Wuhan 4.0074. china) Department of Physics Huazhong University of Science and Technology Wuhan 430074 China Department of Mathematics Huazhong University of Science and Technology Wuhan 430074 China institute of geodesy and geophysics Chinese Academy of Sciences Wuhan 430077 China

Based on the measurement principles of GRACE satellites, the observation equations are set up using the energy balance approach. The Earth's gravitational field complete up to degree and order 120 is recovered applying the preconditioning conjugate gradient iterative approach by numerical simulation. Assuming an accuracy of 1 μm/s in range-rate measurements of the K-band microwave ranging system, the matching relationships of accuracies of K-band microwave ranging system, SuperSTAR Accelerometer, position vector and velocity vector measurements are investigated.

关键词： the Earth’s gravitational field GRACE satellites energy balance approach preconditioning conjugate gradient method.

Separation of systematic errors in processing high precision GPS baselines

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中国有色金属学会会刊：英文版 2005年第S1期15卷 139-141页

作者： WANG Zhen-jie~(1, 2), QU Guo-qing~2 (1. institute of Architectural Engineering, Shangdong University of Technology, Zibo 255012, china 2. institute of geodesy and {4., chinese academy of sciences, Wuhan 4.0077,china) Shandong Univ Technol Inst Architectural Engn Zibo 255012 Peoples R China chinese Acad Sci Inst Geodesy & Geophys Wuhan 430077 Peoples R China

The research is based on the double difference observations and semi-parametric model. Systematic errors are considered as the parameters to be estimated, and brought into the GPS observation equations. High precision baselines are obtained after separating systematic errors. The crucial steps are choosing regularizer and regularization parameters in processing GPS systematic errors by using the semi-parametric model. We propose a new regularizer and apply it to dealing with systematic errors. Also, we compare it with one proposed by other researchers. This comparison is done when all the regularization parameters equal to one. The computation result of the example shows that two regularizers correspond well and they can separate systematic errors successfully. Thus, we can get high precision baselines. Compared with R=QK-1Q′, our regularizer R=GTG is simple, so, the process of resolving the high precision baselines is relatively simple.

关键词： GPS systematic errors semi-parametric model regularizer

Determination of ocean tide loading displacements in Hong Kong using GPS technique

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Science china Earth sciences 2010年第7期53卷 993-1007页

作者： YUAN LinGuo1,3, DING XiaoLi1, SUN HePing2, ZHONG Ping1,3 & CHEN Wu1 1 Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, china 2 Key Laboratory of Dynamic geodesy, institute of geodesy and {4., chinese academy of sciences, Wuhan 4.0077, china 3 Department of Surveying Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, china Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic University Kowloon Hong Kong China Department of Surveying Engineering School of Civil Engineering Southwest Jiaotong University Chengdu China Key Laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China

Ocean tide loading (OTL) displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations. Parameters of the OTL displacements were estimated using daily GPS solutions obtained with precise point positioning (PPP) technique. The results were compared with predictions from seven latest global ocean tide models. Gravity measurements of OTL in Hong Kong were also used to validate the GPS results. The study shows that the results from both the GPS and gravity measurements agree best with the GOT4.7 and NAO99b models, when the K1 and K2 constituents are excluded. The agreements between the GPS and the model estimates are generally at sub-millimeter level in both the horizontal and vertical directions, except for S2, K2 and K1 constituents that have relatively larger errors. After removing the systematic biases between the GPS and the model estimates, the misfits of M2, S2, N2, O1, P1 and Q1 at all sites are within 0.5 and 1.0 mm in the horizontal and the vertical directions, respectively, whereas K1 and K2 show relatively larger misfits of up to 2.3 mm. Both the GPS and the gravity S2 estimates have large biases with unknown reasons when compared with the modeled values, which needs to be further investigated. The study demonstrates that GPS is capable of estimating the OTL displacements with the same accuracy as the model predictions, especially for coastal areas.

关键词： GPS ocean tide loading ocean tide model site displacement

Preliminary results and analyses of using IGS GPS data to determine global ionospheric TEC

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Progress in Natural Science:Materials International 2003年第6期 48-52页

作者： YUAN Yunbin and OU Jikun(Laboratory of Dynamic geodesy, institute of geodesy and geophysics,{4., Wuhan 4.0077, china) Laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China

Using the spherical harmonic (SH) function model and the dual frequency GPS data of 139 International GPS Service (IGS) stations for July 15 of 2000, the global ionospheric total electron content (TEC) is calculated and the basic method is investigated. Here, preliminary results are reported and the problems and difficulties to be solved for using GPS data to determine the global ionospheric TEC are discussed.

关键词： global positioning system spherical harmonic function model ionospheric delay total electron content.