局部区域模型重力异常快速算法

地球重力场位系数模型可以用于计算局部重力扰动场元。然而随着地球重力场模型阶次的提高、局域重力场计算范围的增大,其计算速度往往不能满足工程需求。针对这一问题,在对位系数模型泰勒级数展开的基础上提出了采用向量运算、混合编程的方法,同时对连带勒让德函数Belikov递推方法中与经纬度无关的量进行了预先计算,有效提高了计算速度。提出的方法对于利用超高阶次重力场模型快速解算大范围、高分辨率重力场元数据以及累加求和计算具有一定的参考与借鉴意义。     

利用FFT技术计算垂线偏差研究

首先导出了更加严密的二维平面FFT垂线偏差计算公式,在深入分析和比较二维平面和二维球面FFT算法特点和差异的基础上,给出了二维球面FFT计算公式的改进形式,并通过大量的数值计算,详细讨论了参考场选取、积分球冠半径确定、边缘效应、积分元离散化误差以及计算点奇异积分处理对垂线偏差计算结果的作用和影响。最后,利用全国5'×5'实测重力异常对我国海陆垂线偏差进行了试算,并将计算结果同实际观测值作了比较。     

根据地球重力场模型计算网格剩余垂线偏差

本文介绍一种根据重力场模型计算网格剩余垂线偏差的方法，导出了一组计算完全正规化连带勒让德函数积分的实用公式，经卫星测高数据处理的实际应用，证明这种方法是有效的。     

垂线偏差测量的固体潮和海潮改正

垂线偏差是大地测量学和地球物理学的基础数据。固体潮和海潮是影响高精度垂线偏差测量的重要因素,固体潮改正主要表现为天体引潮位对垂线偏差的直接影响及造成地球形变而产生的附加位对其的间接影响。本文基于引力场球谐展开理论,推导了垂线偏差测量中固体潮和海潮的改正公式。利用JPL DE421星历和EOT11A海潮模型,计算全球19 570个GNSS测站处垂线偏差的潮汐改正值,分析了垂线偏差潮汐改正的时空变化规律。通过实例给出了日、月引潮位及附加位、海潮对垂线偏差子午和卯酉分量的改正。现有高精度垂线偏差测量精度已达到0.1″,而固体潮和海潮对垂线偏差的改正总量级可达我国一等天文规定精度(0.3″)的17%,因此在高精度的垂线偏差应用中需要顾及潮汐改正。     

EGM2008重力场模型计算中国地区垂线偏差分析

分析EGM2008重力场模型的特点,对这个模型进行了较为详细的描述。利用我国900个一等天文点数据与重力场模型EGM2008计算的垂线偏差,分不同阶次和东部、西部地区进行了精度分析和统计,并得出了一些结论。     

我国陆地垂线偏差的精化计算

主要阐述了全国局部地形改正和1′×1′平均法耶异常的计算方法;重力资料充分地区和重力资料不充分地区的垂线偏差计算方法。用214个天文点的天文大地垂线偏差与本文相应方法计算的垂线偏差的不符值,算得的4地区垂线偏差中误差平均值小于±2″。     

中国陆海任意点垂线偏差的快速确定及精度分析

采用全国 14 89个高精度天文大地点作为外部精度检核点 ,对由 1′× 1′垂线偏差数字模型快速确定我国任意点垂线偏差的精度进行了估计。结果表明 ,我国垂线偏差子午和卯酉分量的精度 :东部地区分别为±0 .94″和± 0 .99″ ,西北地区分别为± 1.71″和± 1.2 8″ ,西南地区分别为± 1.95″和± 2 .0 0″。全国垂线偏差总体精度优于± 1.5″。由 1′× 1′垂线偏差数字模型及相应软件确定任意点结果一般只需 2s     

附加垂线偏差和大气折光参数的三维网平差问题

本文探讨了附加垂线偏差和大气折光参数的三维网平差问题;运用F检验,引进S运算来选取垂线偏差附加参数,从而建立了合理的三维网平差函数模型。     

按克林索求和计算大地水准面差距垂线偏差及重力异常

本文采用克林索求和的方法,应用三个重力模型计算了东经80°~120°和北纬20°~40°之间的大地水准面差距、垂线偏差和重力异常。各模型截取到22阶次为止,并且将各模型计算的5°×5°大地水准面差距和垂线偏差平均值进行了比较。另外还对模型计算的平均重力异常与实测的平均重力异常进行了比较。     

联合多代卫星测高数据建立高分辨率浙江近海垂线偏差模型

联合多代卫星测高数据,研究共线平均理论,在时域上削弱测高数据短波误差影响。基于EGM2008重力场模型及DTU10海面地形模型,采用沿轨迹加权最小二乘方法,确定浙江近海2.5′×2.5′分辨率格网点垂线偏差子午分量ξ和卯酉分量η,将所得计算结果与EGM96、EGM2008、ITG-Grace2010s模型值进行比较。结果表明:浙江近海垂线偏差模型与EGM2008模型的精度较为相近,在子午圈及卯酉圈上的RMS分别为±0.15320″、±0.63061″。     

四面体格网模型的三维拓扑关系计算

四面体格网(TEN)模型是一种重要的空间数据构模方法,侧重于三维空间对象内部的表达,但是存在着数据量大、计算速度慢的问题。三维拓扑关系是三维GIS的重要研究内容,为此,该文提出了面向TEN的三维拓扑关系计算方法。基于点集拓扑学理论,将TEN分解为内部、边界和外部3个集合,并使用9交模型描述了TEN/TEN的8种拓扑关系;设计了面向TEN的三维拓扑关系计算流程,详细阐述了面向TEN的三维拓扑关系计算的核心算法;基于提出的三维拓扑关系算法,设计了面向TEN的拓扑关系计算实验。实验结果表明:该文提出的面向TEN的三维拓扑关系计算方法,能够满足TEN之间拓扑关系计算的需求。     

基于DEM的地理坐标系下航空摄影技术设计

本文通过分析地形起伏对像片重叠度的影响,提出了在地理坐标系下基于DEM的航空摄影技术设计,研制了的航空摄影技术设计软件系统,将该系统设计的数据结果同实际飞行数据进行了对比,实验证明使用该软件系统敷设的航线像主点更科学、更合理。     

复杂地形条件的地表面积计算软件开发

针对现有地表面积计算软件在计算复杂地形时操作异常繁琐,且所生成三角网为单边界三角网这一问题,开发了一种新的地表面积计算软件。采用C#语言,利用数字地图,按照三角网建立地面模式,通过三角网内高程内插、点坐标集判断和分类等方式,完成待测区域内地表的并行分块与三角网的重建,实现复杂地形条件下的多边界三角网的生成和地表面积的一体化计算,并将区域内各个三角形的编号和面积直接显示于计算机屏幕上。实验结果表明:该软件使用直观方便,操作简单,精度可靠,适用范围广,可以有效地减少计算复杂地形地表面积时的操作步骤,降低工作强度,并能输出面积计算结果的各种信息。     

基于重力场模型统一亚太高程基准的方法研究

针对不同国家和地区高程基准不一致的问题,该文采用GOCE重力场模型和GPS/水准数据对高程基准统一的方法进行了研究,分析了基于GOCE的不同重力场模型用于计算亚太区域(110°E~180°E,50°S~50°N)高程基准偏差的差异,基于重力场模型GECO,利用亚太区域36个验潮站附近的GPS/水准点数据计算的平均海平面与大地水准面垂直偏差的平均值为0.416m,利用日本沿岸5个GPS/水准点数据计算的高程基准与大地水准面垂直偏差的平均值为0.185m,利用澳大利亚沿岸4个GPS/水准点数据计算的高程基准与大地水准面垂直偏差的平均值为0.41m。     

A new trapezoidal-mesh based data model for spatial operations

This paper presents a new spatial data model based on trapezoidal-mesh for implementing spatial operations within geographical information systems (GIS). Based only on the solid foundation of spatial operations, diversified application models can be established to bridge the gap between Digital Earth models and the real world with its real-world problems (‘connecting through location’). In this paper, the involved polygon features are decomposed into a series of trapezoidal-meshes. Then, geo-processing operations are employed on these meshes rather than the original polygon features, resulting in a relatively simple spatial computation. As a kind of model designed by integrating raster with vector, the model presented here has advantages over other models when carrying out spatial operations insofar as providing a solid foundation for achieving the grand goal of Digital Earth. The concept of this data model and the two extensive examples of its application in spatial operations are elaborated upon in this article. As a result, this article and the research that supports it, proves that the adoption of the trapezoidal-mesh model greatly improves the efficiency of spatial operations in GIS.     

A new approach for vegetation change detection in urban areas

Because of complex change in urban areas, modified CVA application based on mask techniques can minify the effect of non-vegetation changes and improve upon efficiency to a great extent. Moreover, drawing from methods in polar plots, the technique measures changes with absolute angular and total magnitude of PVI calculated on the basis of linear fit with least-square estimation and GVI calculated using 3D G-S transformation. Finally, this application is performed with Landsat ETM+ imageries of Wuhan in 2002 and 2005, and assessed by error matrix, in the way it could detect change pixels 94.91% correct, and the total consistent coefficient Kappa and could reach to 0.85. The evaluation result demonstrates this new application trends as an efficient and effective alternative to urban vegetation change extraction.     

A new approach for vegetation change detection in urban areas

IntroductionVegetation distribution and change is regardedas ani mportant sign of urban environment . Withcity expanding and population increasing, herecomes a series of problems on environment ,andmoreover ,greening ratio is regarded as a stand-ard of ci…     

A novel ensemble approach of bivariate statistical-based logistic model tree classifier for landslide susceptibility assessment

Abstract

This study addresses landslide susceptibility mapping (LSM) using a novel ensemble approach of using a bivariate statistical method (weights of evidence [WoE] and evidential belief function [EBF])-based logistic model tree (LMT) classifier. The performance and prediction capability of the ensemble models were assessed using the area under the ROC curve (AUROC), standard error, 95% confidence intervals and significance level P. Model performance analyses indicated that the AUROC values of the WoE–LMT ensemble model using the training and validation data-sets were 86.02 and 85.9%, respectively, whereas those of the EBF–LMT ensemble model were 88.2 and 87.8%, respectively. On the other hand, the AUC curves for the four landslide susceptibility maps indicated that the AUC values of the ensemble models of WoE–LMT (85.11 and 83.98%) and EBF–LMT (86.21 and 85.23%) could improve the performance and prediction accuracy of single WoE (84.23 and 82.46%) and EBF (85.39 and 81.33%) models for the training and validation data-sets.     

A novel approach for constructing a 3D model based on registering a mono image on a 3D model,applicable in Digital Earth

The effect of Digital Earth on our life is vital. Developing and updating Geospatial data in Digital Earth is also essential. This paper presents the application of a new approach of image registration in Digital Earth. The approach was developed based on registering a mono photograph on a master 3D model. The result is a 3D vector model, which can be broadly applied in visualisation, mapping, geographic information system (GIS), planning, change detection, as well as Digital Earth. The approach does not require parameters of correction for transformation. The accuracy of the output depends on the accuracy of the master data. This approach is very versatile and able to register any image on the digital elevation model, digital surface model and topographic 3D model.