The Antarctic geodetic datum constitutes a specialized implementation of the modern geodetic reference system within the extreme polar environment.A high-precision,unified,and dynamic Antarctic geodetic datum serves a...The Antarctic geodetic datum constitutes a specialized implementation of the modern geodetic reference system within the extreme polar environment.A high-precision,unified,and dynamic Antarctic geodetic datum serves as critical infrastructure for polar scientific research and engineering safety.This study reviews the composition,current status,and implementation pathways of the Antarctic geodetic datum through four dimensions:coordinate datum,height datum,gravity datum and sounding datum.Preliminary analysis reveals that the development of the Antarctic geodetic datum framework is severely lagging,thereby failing to meet the demands of both scientific expeditions and polar research.To address these challenges,this study proposes an implementation pathway leveraging the 5th International Polar Year(IPY-5)to pioneer regional high-precision geodetic datum in the China’s key research sector covering the area between Amery Ice Shelf and Princess Elizabeth Land,specially highlighting the Prydz Bay–Amery Ice Shelf–Lambert Glacier–Dome A(PANDA)transect,by deploying multi-technique stations andμGal-level superconducting gravimeter networks;and then to integrate multinational observation resources to ultimately establish a high-precision,unified,and dynamic geodetic datum framework.This framework will deliver a spatiotemporal infrastructure for Antarctica to advance the strategic goals of“understanding,protecting,and utilizing Antarctica”.展开更多
Land subsidence significantly impacts the accuracy of the National Elevation Datum in China.In order to solve this issue,a dynamic and economical way was proposed to update the National Elevation Datum with the assist...Land subsidence significantly impacts the accuracy of the National Elevation Datum in China.In order to solve this issue,a dynamic and economical way was proposed to update the National Elevation Datum with the assistance of InSAR in the North China Plain,which served as the research area.Moreover,the GNSS result was used to correct the InSAR result for the vertical deformation field,which has a relatively unified deformation reference.By integrating the vertical deformation field with the national elevation control point,an analysis and evaluation of changes in the National Elevation Datum were conducted.In addition,a regional remeasurement scheme was formulated to achieve dynamic updates and mainte-nance of the National Elevation Datum on a regional scale.Through data acquisition and processing,we successfully improved reliability within the main subsidence areas for future use.As a result,updating the elevation values utilize a regional update method,and a dynamic and economical technical process to update the National Elevation Datum is shown in the study.展开更多
受限于海底导航信标时间同步的固有难度,水下导航通常采用主动式定位模型。然而,该模型总是不适定的,即每个观测对应载体信号收发时刻的两个待定点。若忽略载体运动,可取0.5倍的信号往返程的传播时间作为观测值进行定位,但这必然引入模...受限于海底导航信标时间同步的固有难度,水下导航通常采用主动式定位模型。然而,该模型总是不适定的,即每个观测对应载体信号收发时刻的两个待定点。若忽略载体运动,可取0.5倍的信号往返程的传播时间作为观测值进行定位,但这必然引入模型误差,特别是在深海场景或载体高速运动的情形下;若使用多普勒测速或惯性导航等航位推算信息,则会导致声呐导航依存于外部信息。因此,提出了一种附加载体运动学参数的主动式声呐时间开窗导航定位模型,实现了载体位置、速度、加速度等信息的联合估计,在实时输出载体当前时刻坐标信息的同时实现了载体任意时刻运动状态信息的获取,解决了主动式定位模型的不适定性问题。同时,提出了时间开窗导航定位精度几何因子(trajectory dilution of precision,TRDOP),以评估时间开窗导航定位构型的强度。结果表明,TRDOP可以很好地刻画时间开窗导航定位构型的优劣,且时间开窗导航定位模型显著优于传统空间交会定位模型。在日本公开数据集上的测试结果显示,主动式声呐时间开窗导航定位模型的导航定位精度优于5 m,且窗口中间时刻的定位精度更高。展开更多
Static corrections using the conventional method are basically conducted in two steps, the weathering correction followed by the correction from the top of the sub-weathering to the unified datum. However, the convent...Static corrections using the conventional method are basically conducted in two steps, the weathering correction followed by the correction from the top of the sub-weathering to the unified datum. However, the conventional method fails to well deal with statics problems in case the top of the sub-weathering is sharply undulated and the lateral velocity of the sub-weathering varies significantly. This brings us to the introduction of a smooth intermediate reference datum （IRD） located under the top of the sub-weathering, which helps to further increase the accuracy of statics based on the weathering corrections, and ensures the imaging quality. Good results based on the IRD technique have been achieved in the complex areas in western China. This paper discusses the IRD functions, its application requirements, and selection of related parameters. Some typical sections for comparison are also given in this paper.展开更多
This paper first develops the approaches to determine the geopotential of the local mean sea level,and then investigates the offset of the 1985 vertical datum surface defined by the mean sea level of Yellow Sea at the...This paper first develops the approaches to determine the geopotential of the local mean sea level,and then investigates the offset of the 1985 vertical datum surface defined by the mean sea level of Yellow Sea at the Dagang Tide Gauge in Qingdao city using the developed approaches and GPS/leveling data.It shows that the geopotential of the local mean sea level at the tide gauge is equal to 62 636 853.5±0.2 m2·s -2 and that the 1985 vertical datum surface is 24.6±5.4 cm above the geoid realized by the geopotential W 0= 62 636 856.0±0.5 m2·s -2.展开更多
针对工业管道与容器在自动化装配、焊接及在线检测过程中,环状端面基准拟合易受边界噪声、局部形变与采样不均影响而导致精度不足的问题,提出一种曲率-拓扑双驱动的端面基准平面拟合方法。该方法基于局部协方差张量的谱分解提取主曲率,...针对工业管道与容器在自动化装配、焊接及在线检测过程中,环状端面基准拟合易受边界噪声、局部形变与采样不均影响而导致精度不足的问题,提出一种曲率-拓扑双驱动的端面基准平面拟合方法。该方法基于局部协方差张量的谱分解提取主曲率,构建平整度与退化度指标,实现点云的非均匀稀疏化;进一步引入拓扑数据分析(Topological Data Analysis,TDA),通过构建Vietoris-Rips复形与持久同调分析提取具有闭合拓扑特征的骨架点集,从而嵌入环形端面的结构先验。基于骨架点集协方差矩阵的最小特征向量确定平面法向,实现高鲁棒性的姿态估计。实验表明,该方法平均绝对角度误差小于0.03°,单次拟合耗时低于0.03 s,相较于最小中值平方法提速约300倍,在主元分析、随机采样一致性等传统方法基础上精度提升约10倍。该方法精度高、鲁棒性强、实时处理速度快,无需人工干预,适用于复杂工业环境下的管道端面自动化定位与基准构建,可为智能制造中的焊接路径规划与在线检测提供可靠技术支撑。展开更多
Considering the drastic variations in the surface elevation of the piedmont region in the Bai Cheng West Area,there is no reference point within the Reference Ground Line(RG line)of the starting point of the synthetic...Considering the drastic variations in the surface elevation of the piedmont region in the Bai Cheng West Area,there is no reference point within the Reference Ground Line(RG line)of the starting point of the synthetic seismic records in the process of calibration of the horizon.Through the analysis of the process and properties of the production of the RG line,in the processing of seismic data,it is indicated that the position of the synthetic data of seismic records is not located at the beginning of the RG line.Rather,it must be at the time point of the seismic profile at the elevation of a datum position of the static value of less than the datum plane.Both the RG line and the elevation static correction value line can easily be seen by computerizing the calculated value of the elevation static correction of the datum plane relating to the seismic section and plotting it on the seismic section.To achieve a good calibration with the synthetic seismogram,it is possible to set the starting point of the synthetic seismogram on the elevation static correction value line that is situated at the place of the Common Mid-Point(CMP).In the current paper,a systematic overview of methods and safety procedures for establishing the seismic interpretation work area and horizon calibration in seismic interpretation has been reviewed,which will form an effective guide towards seismic interpretation under the complicated surface conditions in the Bai Cheng west region.展开更多
We analyze the characteristics of different floating datums for static corrections and discuss the methods for determining them. The effect of different floating datum corrections was studied using theoretical model e...We analyze the characteristics of different floating datums for static corrections and discuss the methods for determining them. The effect of different floating datum corrections was studied using theoretical model experiments, resulting in the conclusion that the velocity obtained after the floating datum correction with the minimum static correction errors depends on the velocity of the layer below the low velocity layer （LVL） lower boundary and is not related to topographic relief and LVL structure. For the real data processing case, wave equation numerical model experiments were conducted which resulted in a new method for calculating objective functions based on the waveform and modifications to the calculation equation for minimum static correction errors to make the method suitable for real data static correction processing using inhomogeneous velocity models with lower velocity boundary relief. Real data processing results demonstrate the method＇s superiority.展开更多
This study focuses on spatial autocorrelation and the spatial distribution of urban land prices from a regional perspective.Taking Hubei province,China,as a case study area,spatial autocorrelation degree,spatial autoc...This study focuses on spatial autocorrelation and the spatial distribution of urban land prices from a regional perspective.Taking Hubei province,China,as a case study area,spatial autocorrelation degree,spatial autocorrelation pattern,and the mechanism of its formation were discussed.The study employs Moran’s I,local Moran’s I,and Moran’s I correlogram to analyze spatial autocorrelation degree and its change along with contiguity order.Some local clustering hot spots are found.This paper uses semi-variance statistic for land price based on route distance to find the spatial autocorrelation scale.We also adopt spatial clustering based on a kind of composite distance to probe into the clustering characteristic of land prices.By Moran’s I and Moran’s I correlogram,we find that datum price of the cities in Hubei province has faint spatial autocorrelation degree at the first and the second-order contiguity.Spatial variance hints that the scale of the autocorrelation is about 200 km in route distance.Spatial clustering result indicates that the spatial distribution of city land price is a kind of hierarchy structure similar to administrative regions.From principal factors analysis and stepwise linear regression,we find that the value added of city secondary and tertiary industry and the urban population are two of the most influential factors to urban datum land price.The value added of city secondary and tertiary industry has higher spatial autocorrelation than urban datum land price and has a bigger autocorrelation scale.But urban population has little spatial autocorrelation.It can be inferred that the spatial autocorrelation of urban land price is mainly caused by economic spatial autocorrelation.But its spatial autocorrelation degree is lower than economic factors because urban datum land price is also influenced by other special local factors,such as population,city infrastructure,land supply,etc.展开更多
When topography and low velocity zone differences vary greatly, conventional vertical static time shifts will cause wavefield distortion and influence wave equation seismic imaging for seismic data acquired on a compl...When topography and low velocity zone differences vary greatly, conventional vertical static time shifts will cause wavefield distortion and influence wave equation seismic imaging for seismic data acquired on a complex near surface. In this paper, we propose an approach to datum correction that combines a joint tomography inversion with wavefield continuation to solve the static problem for seismic data on rugged acquisition topography. First, the near surface model is obtained by refracted wave tomography inversion. Second, the wavefield of sources and receivers are continued downward and upward to accomplish datum correction starting from a flat surface and locating the datum above topography. Based on the reciprocal theorem, Huygens＇ and Fresnel principles, the location of sources and receivers, and regarding the recorded data on the surface as a secondary emission, the sources and receivers are upward-continued to the datum above topography respectively. Thus, the datum correction using joint tomography inversion and wavefield continuation with the condition of a complex near surface is accomplished.展开更多
The Gauss-Markov （GM） model and the Errors-in-Variables （EIV） model are frequently used to perform 3D coordinate transformations in geodesy and engineering surveys. In these applications, because the observation e...The Gauss-Markov （GM） model and the Errors-in-Variables （EIV） model are frequently used to perform 3D coordinate transformations in geodesy and engineering surveys. In these applications, because the observation errors in original coordinates system are also taken into account, the latter is more accurate and reasonable than the former. Although the Weighted Total Least Squares （WTLS） technique has been intro- duced into coordinate transformations as the measured points are heteroscedastic and correlated, the Variance- Covariance Matrix （VCM） of observations is restricted by a particular structure, namely, only the correlations of each points are taken into account. Because the 3D datum transformation with large rotation angle is a non- linear problem, the WTLS is no longer suitable in this ease. In this contribution, we suggested the nonlinear WTLS adjustments with equality constraints （NWTLS-EC） for 3D datum transformation with large rotation an- gle, which removed the particular structure restriction on the VCM. The Least Squares adjustment with Equality （LSE） constraints is employed to solve NWTLS-EC as the nonlinear model has been linearized, and an iterative algorithm is proposed with the LSE solution. A simulation study of 3D datum transformation with large rotation angle is given to insight into the feasibility of our algorithm at last.展开更多
The contribution presents the representative research progress on global static gravity field modeling,regional geoid/quasigeoid determination,vertical datum study,as well as the theory,algorithm and software for grav...The contribution presents the representative research progress on global static gravity field modeling,regional geoid/quasigeoid determination,vertical datum study,as well as the theory,algorithm and software for gravity field study in China from 2019 to 2023,which are the highlights of the chapter 6“Progress in Earth Gravity Model and Vertical Datum”in the“2019—2023 China National Report on Geodesy”that submitted to the International Association of Geodesy(IAG).In addition,suggestions are proposed to promote the research in the fields of earth gravity field,geoid/quasigeoid and vertical datumin China according to trends of international geodesy and related disciplines.展开更多
In this article, we study the Cauchy problem for the linearized spatially homogeneous non-cutoff Boltzamnn equation with Maxwellian molecules. By using the spectral decomposition, we solve the Cauchy problem with init...In this article, we study the Cauchy problem for the linearized spatially homogeneous non-cutoff Boltzamnn equation with Maxwellian molecules. By using the spectral decomposition, we solve the Cauchy problem with initial datum in the sense of distribution, which contains the dual space of a Gelfand-Shilov class. We also prove that this solution belongs to the Gelfand-Shilov space for any positive time.展开更多
A balance of urban datum land prices is achieved to harmonize regional land prices and make the prices truly reflect different economic development levels and land prices among cities. The current piecewise linear int...A balance of urban datum land prices is achieved to harmonize regional land prices and make the prices truly reflect different economic development levels and land prices among cities. The current piecewise linear interpolation balance method widely used has two drawbacks that always lead to an unsatisfactory balance among some cities. When the excess of land price in the central city to the surrounding zone reaches a certain degree, land price in the circumjacent city is not only consistent with the local land grade and land use level, but also influenced by the diffusion of land price in the central city. Thus, a new balanced scheme of datum land prices based on the city gravitation model and stochastic diffusion equation is brought forward. Finally, the new method is examined in the practice of datum land price balance in Hubei Province, China.展开更多
Precise Point Positioning (PPP) is traditionally based on dual-frequency observations of GPS or GPS/GLONASS satellite navigation systems. Recently, new GNSS constellations, such as the European Galileo and the Chinese...Precise Point Positioning (PPP) is traditionally based on dual-frequency observations of GPS or GPS/GLONASS satellite navigation systems. Recently, new GNSS constellations, such as the European Galileo and the Chinese BeiDou are developing rapidly. With the new IGS project known as IGS MGEX which produces highly accurate GNSS orbital and clock products, multi-constellations PPP becomes feasible. On the other hand, the un-differenced ionosphere-free is commonly used as standard precise point positioning technique. However, the existence of receiver and satellite biases, which are absorbed by the ambiguities, significantly affected the convergence time. Between-satellite-single-difference (BSSD) ionosphere free PPP technique is traditionally used to cancel out the receiver related biases from both code and phase measurements. This paper introduces multiple ambiguity datum (MAD) PPP technique which can be applied to separate the code and phase measurements removing the receiver and satellite code biases affecting the GNSS receiver phase clock and ambiguities parameters. The mathematical model for the three GNSS PPP techniques is developed by considering the current full GNSS constellations. In addition, the current limitations of the GNSS PPP techniques are discussed. Static post-processing results for a number of IGS MGEX GNSS stations are presented to investigate the contribution of the newly GNSS system observations and the newly developed GNSS PPP techniques and its limitations. The results indicate that the additional Galileo and BeiDou observations have a marginal effect on the positioning accuracy and convergence time compared with the existence combined GPS/GLONASS PPP. However, reference to GPS PPP, the contribution of BeiDou observations can be considered geographically dependent. In addition, the results show that the BSSD PPP models slightly enhance the convergence time compared with other PPP techniques. However, both the standard un-differenced and the developed multiple ambiguity datum techniques present comparable positioning accuracy and convergence time due to the lack of code and phase-based satellite clock products and the mathematical correlation between the positioning and ambiguity parameters.展开更多
The vertical datum of China is composed of leveling datum for heights and chart datum for depths.The determination of national leveling datum and its disadvantages were discussed firstly.The local mean sea level and c...The vertical datum of China is composed of leveling datum for heights and chart datum for depths.The determination of national leveling datum and its disadvantages were discussed firstly.The local mean sea level and chart datum with its guarantee rate of navigation safety were studied secondly.The models of unification of national surveying vertical datum,such as optimization model of mean sea level,adoption of New Chinese quasi-geoid of 2000(CQG2000)and time-invariant global geoid were suggested finally.展开更多
文摘The Antarctic geodetic datum constitutes a specialized implementation of the modern geodetic reference system within the extreme polar environment.A high-precision,unified,and dynamic Antarctic geodetic datum serves as critical infrastructure for polar scientific research and engineering safety.This study reviews the composition,current status,and implementation pathways of the Antarctic geodetic datum through four dimensions:coordinate datum,height datum,gravity datum and sounding datum.Preliminary analysis reveals that the development of the Antarctic geodetic datum framework is severely lagging,thereby failing to meet the demands of both scientific expeditions and polar research.To address these challenges,this study proposes an implementation pathway leveraging the 5th International Polar Year(IPY-5)to pioneer regional high-precision geodetic datum in the China’s key research sector covering the area between Amery Ice Shelf and Princess Elizabeth Land,specially highlighting the Prydz Bay–Amery Ice Shelf–Lambert Glacier–Dome A(PANDA)transect,by deploying multi-technique stations andμGal-level superconducting gravimeter networks;and then to integrate multinational observation resources to ultimately establish a high-precision,unified,and dynamic geodetic datum framework.This framework will deliver a spatiotemporal infrastructure for Antarctica to advance the strategic goals of“understanding,protecting,and utilizing Antarctica”.
基金supported by the Scientific and Technological Innovation Project of SHASG(SCK2022-01)National Key Research and Development Program of China(2016YFC0803109)。
文摘Land subsidence significantly impacts the accuracy of the National Elevation Datum in China.In order to solve this issue,a dynamic and economical way was proposed to update the National Elevation Datum with the assistance of InSAR in the North China Plain,which served as the research area.Moreover,the GNSS result was used to correct the InSAR result for the vertical deformation field,which has a relatively unified deformation reference.By integrating the vertical deformation field with the national elevation control point,an analysis and evaluation of changes in the National Elevation Datum were conducted.In addition,a regional remeasurement scheme was formulated to achieve dynamic updates and mainte-nance of the National Elevation Datum on a regional scale.Through data acquisition and processing,we successfully improved reliability within the main subsidence areas for future use.As a result,updating the elevation values utilize a regional update method,and a dynamic and economical technical process to update the National Elevation Datum is shown in the study.
文摘受限于海底导航信标时间同步的固有难度,水下导航通常采用主动式定位模型。然而,该模型总是不适定的,即每个观测对应载体信号收发时刻的两个待定点。若忽略载体运动,可取0.5倍的信号往返程的传播时间作为观测值进行定位,但这必然引入模型误差,特别是在深海场景或载体高速运动的情形下;若使用多普勒测速或惯性导航等航位推算信息,则会导致声呐导航依存于外部信息。因此,提出了一种附加载体运动学参数的主动式声呐时间开窗导航定位模型,实现了载体位置、速度、加速度等信息的联合估计,在实时输出载体当前时刻坐标信息的同时实现了载体任意时刻运动状态信息的获取,解决了主动式定位模型的不适定性问题。同时,提出了时间开窗导航定位精度几何因子(trajectory dilution of precision,TRDOP),以评估时间开窗导航定位构型的强度。结果表明,TRDOP可以很好地刻画时间开窗导航定位构型的优劣,且时间开窗导航定位模型显著优于传统空间交会定位模型。在日本公开数据集上的测试结果显示,主动式声呐时间开窗导航定位模型的导航定位精度优于5 m,且窗口中间时刻的定位精度更高。
文摘Static corrections using the conventional method are basically conducted in two steps, the weathering correction followed by the correction from the top of the sub-weathering to the unified datum. However, the conventional method fails to well deal with statics problems in case the top of the sub-weathering is sharply undulated and the lateral velocity of the sub-weathering varies significantly. This brings us to the introduction of a smooth intermediate reference datum （IRD） located under the top of the sub-weathering, which helps to further increase the accuracy of statics based on the weathering corrections, and ensures the imaging quality. Good results based on the IRD technique have been achieved in the complex areas in western China. This paper discusses the IRD functions, its application requirements, and selection of related parameters. Some typical sections for comparison are also given in this paper.
文摘This paper first develops the approaches to determine the geopotential of the local mean sea level,and then investigates the offset of the 1985 vertical datum surface defined by the mean sea level of Yellow Sea at the Dagang Tide Gauge in Qingdao city using the developed approaches and GPS/leveling data.It shows that the geopotential of the local mean sea level at the tide gauge is equal to 62 636 853.5±0.2 m2·s -2 and that the 1985 vertical datum surface is 24.6±5.4 cm above the geoid realized by the geopotential W 0= 62 636 856.0±0.5 m2·s -2.
文摘针对工业管道与容器在自动化装配、焊接及在线检测过程中,环状端面基准拟合易受边界噪声、局部形变与采样不均影响而导致精度不足的问题,提出一种曲率-拓扑双驱动的端面基准平面拟合方法。该方法基于局部协方差张量的谱分解提取主曲率,构建平整度与退化度指标,实现点云的非均匀稀疏化;进一步引入拓扑数据分析(Topological Data Analysis,TDA),通过构建Vietoris-Rips复形与持久同调分析提取具有闭合拓扑特征的骨架点集,从而嵌入环形端面的结构先验。基于骨架点集协方差矩阵的最小特征向量确定平面法向,实现高鲁棒性的姿态估计。实验表明,该方法平均绝对角度误差小于0.03°,单次拟合耗时低于0.03 s,相较于最小中值平方法提速约300倍,在主元分析、随机采样一致性等传统方法基础上精度提升约10倍。该方法精度高、鲁棒性强、实时处理速度快,无需人工干预,适用于复杂工业环境下的管道端面自动化定位与基准构建,可为智能制造中的焊接路径规划与在线检测提供可靠技术支撑。
文摘Considering the drastic variations in the surface elevation of the piedmont region in the Bai Cheng West Area,there is no reference point within the Reference Ground Line(RG line)of the starting point of the synthetic seismic records in the process of calibration of the horizon.Through the analysis of the process and properties of the production of the RG line,in the processing of seismic data,it is indicated that the position of the synthetic data of seismic records is not located at the beginning of the RG line.Rather,it must be at the time point of the seismic profile at the elevation of a datum position of the static value of less than the datum plane.Both the RG line and the elevation static correction value line can easily be seen by computerizing the calculated value of the elevation static correction of the datum plane relating to the seismic section and plotting it on the seismic section.To achieve a good calibration with the synthetic seismogram,it is possible to set the starting point of the synthetic seismogram on the elevation static correction value line that is situated at the place of the Common Mid-Point(CMP).In the current paper,a systematic overview of methods and safety procedures for establishing the seismic interpretation work area and horizon calibration in seismic interpretation has been reviewed,which will form an effective guide towards seismic interpretation under the complicated surface conditions in the Bai Cheng west region.
文摘We analyze the characteristics of different floating datums for static corrections and discuss the methods for determining them. The effect of different floating datum corrections was studied using theoretical model experiments, resulting in the conclusion that the velocity obtained after the floating datum correction with the minimum static correction errors depends on the velocity of the layer below the low velocity layer （LVL） lower boundary and is not related to topographic relief and LVL structure. For the real data processing case, wave equation numerical model experiments were conducted which resulted in a new method for calculating objective functions based on the waveform and modifications to the calculation equation for minimum static correction errors to make the method suitable for real data static correction processing using inhomogeneous velocity models with lower velocity boundary relief. Real data processing results demonstrate the method＇s superiority.
基金This research was funded by the National Natural Science Foundation of China(Nos.41171312 and 40901188).
文摘This study focuses on spatial autocorrelation and the spatial distribution of urban land prices from a regional perspective.Taking Hubei province,China,as a case study area,spatial autocorrelation degree,spatial autocorrelation pattern,and the mechanism of its formation were discussed.The study employs Moran’s I,local Moran’s I,and Moran’s I correlogram to analyze spatial autocorrelation degree and its change along with contiguity order.Some local clustering hot spots are found.This paper uses semi-variance statistic for land price based on route distance to find the spatial autocorrelation scale.We also adopt spatial clustering based on a kind of composite distance to probe into the clustering characteristic of land prices.By Moran’s I and Moran’s I correlogram,we find that datum price of the cities in Hubei province has faint spatial autocorrelation degree at the first and the second-order contiguity.Spatial variance hints that the scale of the autocorrelation is about 200 km in route distance.Spatial clustering result indicates that the spatial distribution of city land price is a kind of hierarchy structure similar to administrative regions.From principal factors analysis and stepwise linear regression,we find that the value added of city secondary and tertiary industry and the urban population are two of the most influential factors to urban datum land price.The value added of city secondary and tertiary industry has higher spatial autocorrelation than urban datum land price and has a bigger autocorrelation scale.But urban population has little spatial autocorrelation.It can be inferred that the spatial autocorrelation of urban land price is mainly caused by economic spatial autocorrelation.But its spatial autocorrelation degree is lower than economic factors because urban datum land price is also influenced by other special local factors,such as population,city infrastructure,land supply,etc.
基金the National Development and Innovation Committee Program (2005) 2372the National High-tech R&D Program (863 Program) 2006AA06Z241 of ChinaYouth Innovation Fund of CNPC’ Prestack Imaging Integral Study for Complex near Surface.
文摘When topography and low velocity zone differences vary greatly, conventional vertical static time shifts will cause wavefield distortion and influence wave equation seismic imaging for seismic data acquired on a complex near surface. In this paper, we propose an approach to datum correction that combines a joint tomography inversion with wavefield continuation to solve the static problem for seismic data on rugged acquisition topography. First, the near surface model is obtained by refracted wave tomography inversion. Second, the wavefield of sources and receivers are continued downward and upward to accomplish datum correction starting from a flat surface and locating the datum above topography. Based on the reciprocal theorem, Huygens＇ and Fresnel principles, the location of sources and receivers, and regarding the recorded data on the surface as a secondary emission, the sources and receivers are upward-continued to the datum above topography respectively. Thus, the datum correction using joint tomography inversion and wavefield continuation with the condition of a complex near surface is accomplished.
基金supported by the National Natural Science Foundation of China(41074017)
文摘The Gauss-Markov （GM） model and the Errors-in-Variables （EIV） model are frequently used to perform 3D coordinate transformations in geodesy and engineering surveys. In these applications, because the observation errors in original coordinates system are also taken into account, the latter is more accurate and reasonable than the former. Although the Weighted Total Least Squares （WTLS） technique has been intro- duced into coordinate transformations as the measured points are heteroscedastic and correlated, the Variance- Covariance Matrix （VCM） of observations is restricted by a particular structure, namely, only the correlations of each points are taken into account. Because the 3D datum transformation with large rotation angle is a non- linear problem, the WTLS is no longer suitable in this ease. In this contribution, we suggested the nonlinear WTLS adjustments with equality constraints （NWTLS-EC） for 3D datum transformation with large rotation an- gle, which removed the particular structure restriction on the VCM. The Least Squares adjustment with Equality （LSE） constraints is employed to solve NWTLS-EC as the nonlinear model has been linearized, and an iterative algorithm is proposed with the LSE solution. A simulation study of 3D datum transformation with large rotation angle is given to insight into the feasibility of our algorithm at last.
基金National Key R&D Program of China(Nos.2021YFB3900200,2021YFB3900203)。
文摘The contribution presents the representative research progress on global static gravity field modeling,regional geoid/quasigeoid determination,vertical datum study,as well as the theory,algorithm and software for gravity field study in China from 2019 to 2023,which are the highlights of the chapter 6“Progress in Earth Gravity Model and Vertical Datum”in the“2019—2023 China National Report on Geodesy”that submitted to the International Association of Geodesy(IAG).In addition,suggestions are proposed to promote the research in the fields of earth gravity field,geoid/quasigeoid and vertical datumin China according to trends of international geodesy and related disciplines.
基金supported by the Fundamental Research Funds for the Central Unversities and National Science Foundation of China(11171261and 11422106)
文摘In this article, we study the Cauchy problem for the linearized spatially homogeneous non-cutoff Boltzamnn equation with Maxwellian molecules. By using the spectral decomposition, we solve the Cauchy problem with initial datum in the sense of distribution, which contains the dual space of a Gelfand-Shilov class. We also prove that this solution belongs to the Gelfand-Shilov space for any positive time.
文摘A balance of urban datum land prices is achieved to harmonize regional land prices and make the prices truly reflect different economic development levels and land prices among cities. The current piecewise linear interpolation balance method widely used has two drawbacks that always lead to an unsatisfactory balance among some cities. When the excess of land price in the central city to the surrounding zone reaches a certain degree, land price in the circumjacent city is not only consistent with the local land grade and land use level, but also influenced by the diffusion of land price in the central city. Thus, a new balanced scheme of datum land prices based on the city gravitation model and stochastic diffusion equation is brought forward. Finally, the new method is examined in the practice of datum land price balance in Hubei Province, China.
文摘Precise Point Positioning (PPP) is traditionally based on dual-frequency observations of GPS or GPS/GLONASS satellite navigation systems. Recently, new GNSS constellations, such as the European Galileo and the Chinese BeiDou are developing rapidly. With the new IGS project known as IGS MGEX which produces highly accurate GNSS orbital and clock products, multi-constellations PPP becomes feasible. On the other hand, the un-differenced ionosphere-free is commonly used as standard precise point positioning technique. However, the existence of receiver and satellite biases, which are absorbed by the ambiguities, significantly affected the convergence time. Between-satellite-single-difference (BSSD) ionosphere free PPP technique is traditionally used to cancel out the receiver related biases from both code and phase measurements. This paper introduces multiple ambiguity datum (MAD) PPP technique which can be applied to separate the code and phase measurements removing the receiver and satellite code biases affecting the GNSS receiver phase clock and ambiguities parameters. The mathematical model for the three GNSS PPP techniques is developed by considering the current full GNSS constellations. In addition, the current limitations of the GNSS PPP techniques are discussed. Static post-processing results for a number of IGS MGEX GNSS stations are presented to investigate the contribution of the newly GNSS system observations and the newly developed GNSS PPP techniques and its limitations. The results indicate that the additional Galileo and BeiDou observations have a marginal effect on the positioning accuracy and convergence time compared with the existence combined GPS/GLONASS PPP. However, reference to GPS PPP, the contribution of BeiDou observations can be considered geographically dependent. In addition, the results show that the BSSD PPP models slightly enhance the convergence time compared with other PPP techniques. However, both the standard un-differenced and the developed multiple ambiguity datum techniques present comparable positioning accuracy and convergence time due to the lack of code and phase-based satellite clock products and the mathematical correlation between the positioning and ambiguity parameters.
文摘The vertical datum of China is composed of leveling datum for heights and chart datum for depths.The determination of national leveling datum and its disadvantages were discussed firstly.The local mean sea level and chart datum with its guarantee rate of navigation safety were studied secondly.The models of unification of national surveying vertical datum,such as optimization model of mean sea level,adoption of New Chinese quasi-geoid of 2000(CQG2000)and time-invariant global geoid were suggested finally.
