基于拓扑相似性的道路网综合模型

针对道路网综合时须保持道路网眼空间分布特征这一基本要求,在讨论道路网眼拓扑形式化描述的基础上提出了一种基于拓扑相似性的道路网综合模型。该模型通过制定道路网拓扑相似性评价指标来进行道路网综合方案选择,同时针对拓扑相似性相同的不同道路删除方案,进一步提出了利用道路形状加以评价的方法。结果表明,该模型原理正确,无论对于保持道路网眼空间分布还是形状特征都具有很好的效果。     

面向多源地理空间数据的知识图谱构建

知识图谱广泛应用于人工智能领域,基于此融合多源地理空间数据并表示地理事物的语义和时空信息,实现“数据—知识”的转换成为人们关注的热点。但现有通用知识图谱的空间知识覆盖度低且存在错误,同时基于维基百科构建的地理知识图谱存在空间关系、中文属性和坐标信息等属性缺失问题。因此本文以地理空间数据和百度百科数据的特征分析为基础,提出了以地理空间数据提取地理实体为主,百度百科补充属性信息为辅的知识图谱构建方式。① 基于GeoSparql设计模式层的地理实体、要素、几何形状和空间关系的逻辑关系;② 通过地理实体提取、实体链接和属性信息填充,在数据层实现空间知识融合;③ 结合关系型数据库和图数据库,设计空间知识存储方式;④ 在实体和关系2个方面定量分析知识图谱的构建规模。结果表明,本文构建的知识图谱中地理实体覆盖度和链接百科成功率相对较高,扩充了地理实体的概念描述信息,并将地理坐标的覆盖率提高到100%,对地理数据到地理知识的拓展具有重要意义。     

土地集约利用评价数据库建设与质量控制研究

土地集约利用评价数据库能够归集有关土地利用资料,是对土地进行科学管理的基础。本文以邹平经济技术开发区为例,基于Arc GIS软件平台,依据2014年度《开发区土地集约利用评价数据库标准》的要求进行土地集约利用评价数据库的建设,总结了土地集约利用评价数据库建设的有效方法、建设过程中出现的典型问题及出现问题的原因,并提出解决方案,不仅保证了数据的准确性,同时也提高了数据库建设的工作效率。     

The topological viewshed: embedding topological pointers into digital terrain models to improve GIS capability for visual landscape analysis

The effort to develop a Digital Earth has made dramatic progress in terms of visualisation and visual data integration for use-cases which demand semantically rich analysis. To provide this analysis and ensure legitimate representations of the spatial data from which visualisation are derived, it is necessary to provide more comprehensive analytical capabilities of the view. Questions of aesthetic valuation of landscape require a richer analytical response than simply ‘whether and possibly how much of’ an object or area of land can be seen. It requires interrogation of the scene as it appears and to distinguish between transient visual effects and those locally invariant to view point change. This paper explores a data structure to support scene analytics. As such, it first reviews the existing techniques from the fields of GIS and computer graphics as to their potential and limitations in providing a qualitatively more nuanced visual analysis. It then introduces a new method of encoding visually apparent relationships into terrain models. A prototype implementation is presented based on the Quad-Edge Triangular Irregular Network, though it is believed that raster or vector implementation would be possible. Although developed primarily with landscape analysis in mind, the method could have wider applicability.     

利用城市骨架线网的道路和居民地联动匹配方法

同名道路或者居民地数据间由于数据一致性程度不高,往往存在较大的几何位置偏差,当对道路或者居民地单独进行匹配时,不利于提高匹配正确率和效率。针对这一问题,本文提出了一种利用城市骨架线网的道路和居民地联动匹配方法。联动匹配即模仿人在读图时通过特征地物和空间关联寻找目标地物的思维过程,将匹配看作是一种特征目标寻找、信息关联传递的推理过程。首先,利用约束Delaunay三角网对地图构建城市骨架线网。然后,通过道路、骨架线、骨架线网眼和居民地之间的拓扑关系建立道路和居民地之间的匹配传递模型。最后,根据该传递模型实现通过道路匹配带动居民地匹配或者通过居民地匹配带动道路匹配的联动匹配。该方法优势在于只要有一种要素的数据一致性比较好,就能带动另一种要素取得很好的匹配效果,同时符合人类进行匹配时的认知过程。     

有向拓扑的河系渐变自动绘制算法

河系渐变绘制是地图制图中水系要素表达的重要方面。针对全自动河系渐变研究较少的现状,该文提出一种基于树状约束stroke特征的河系渐变自动绘制算法。该方法在深入分析有向拓扑的数据结构基础上,重点解决河口模式识别、树状约束stroke特征构建、河系层次关系建立、主支流分级渐变等问题,实现全自动河系渐变,并进行实践测试。结果表明,该算法在地图制图过程中无须对河系河源、河口识别、河系分层和河系渐变进行人工干预,自动化程度高,大幅度提升制图效率,渐变效果优于人工绘制效果。     

Tessellations in GIS: Part I—putting it all together

This article attempts to describe the role of tessellated models of space within the discipline of geographic information systems (GIS)—a speciality coming largely out of geography and land surveying, where there was a strong need to represent information about the land’s surface within a computer system rather than on the original paper maps. We look at some of the basic operations in GIS, including dynamic and kinetic applications. We examine issues of topology and data structures and produce a tessellation model that may be widely applied both to traditional “object” and “field” data types. Based on this framework, it can be argued that tessellation models are fundamental to our understanding and processing of geographical space, and provide a coherent framework for understanding the “space” in which we exist. This first article examines static structures, and a subsequent article looks at “change”—what happens when things move.     

Laboratory and numerical model studies of a negatively-buoyant jet discharged horizontally into a homogeneous rotating fluid

Abstract

The results of laboratory experiments and numerical model simulations are described in which the motion of a round, negatively-buoyant, turbulent jet discharged horizontally above a slope into a rotating homogeneous fluid has been investigated. For the laboratory study, flow visualisation data are presented to show the complex three-dimensional flow fields generated by the discharge. Analysis of the experimental data indicates that the spatial and temporal developments of the flow field are controlled primarily by the lateral and vertical discharge position of the jet (with respect to the bounding surfaces of the container of width W) and the specific momentum (M ₀) and buoyancy (B ₀) fluxes driving the jet. The flow is seen to be characterised by the formation of (i) a primary anticyclonic eddy (PCC) close to the source, (ii) an associated secondary cyclonic eddy (SCE) and (iii) a buoyancy-driven bottom boundary current along the right side boundary wall. For the parameter ranges studied, the size L _{p, s} and spatial location x _{p, s} of the PCC and SCE (and the nose velocity u _N of the boundary current) are shown to be only weakly-dependent upon the value of the mixed parameter M ₀Ω/B ₀, where Ω is the background rotation rate. Both L _p and x _p are shown to scale with the separation distance y?/W of the right side wall (y = 0) from the source (y = y?), both L _s and x _s scale satisfactorily with the length scale l _M (= M ₀ ^3/4/B ₀ ^½) and u _N is determined by the appropriate gravity current speed [(g']₀ H]^½ and the separation distance y?/W.

Numerical model results show good qualitative agreement with the laboratory data with regard to the generation of the PCC, SCE and boundary current as characteristic features of the flow in question. In addition, extension of the numerical model to

diagnose potential vorticity and plume thickness distributions for the laboratory cases allow the differences in momentum-and buoyancy-dominated flows to be clearly delineated. Specifically, the characteristic features of the SCE are shown to be strongly dependent upon the value of M ₀Ω/B ₀ for the buoyant jet flow; not least, the numerical model data are able to confirm the controlling role played by the boundary walls in the laboratory experiments. Quantitative agreement between the numerical and laboratory model data is fair; most significantly, the success of the former model in simulating the dominant flow features from the latter enables the reliable extension of the numerical model to be made to cases of direct oceanic interest.     

基于缓冲区融合的临近节点检查方法研究

临近节点是影响矢量数据质量的关键问题.本文针对数据维度提升带来的高维信息这一特征,将要素节点升级为节点缓冲区,设计实现了基于要素节点缓冲区融合的临近节点检查方法,通过多源数据合并、要素转节点、相同节点融合、缓冲以及缓冲区融合等步骤获得要素节点缓冲区融合面,最后通过面积容差判定出临近节点所在范围.实验证明,算法通用性强,...     

基于ADTD型闪电定位数据的江门闪电特征

利用广东省ADTD(active divectory topology diagrammer)闪电定位系统资料,分析2017-2019年江门地区地闪回击的时空分布特征.结果表明:地闪密度大值分布在江门北部及西部,中部地闪回击密度最低.正地闪回击频次占总回击频次的3.36％,负地闪回击频次占总回击频次的96.64％;月分...