Digital map conflation: a review of the process and a proposal for classification

This article is centred on analysing the state of the art of the conflation processes applied to geospatial databases (GDBs) from heterogeneous sources. The term conflation is used to describe the procedure for the integration of these different data, and conflation methods play an important role in systems for updating GDBs, derivation of new cartographic products, densification of digital elevation models, automatic features extraction and so on. In this article we define extensively each conflation process, its evaluation measures and its main application problems and present a classification of all conflation processes. Finally, we introduce a bibliography which the reader may find useful to further explore the field. It tries to serve as a starting point and direct the reader to characteristic research in this area.     

Ad hoc matching of vectorial road networks

In integration of road maps modeled as road vector data, the main task is matching pairs of objects that represent, in different maps, the same segment of a real-world road. In an ad hoc integration, the matching is done for a specific need and, thus, is performed in real time, where only a limited preprocessing is possible. Usually, ad hoc integration is performed as part of some interaction with a user and, hence, the matching algorithm is required to complete its task in time that is short enough for human users to provide feedback to the application, that is, in no more than a few seconds. Such interaction is typical of services on the World Wide Web and to applications in car-navigation systems or in handheld devices.

Several algorithms were proposed in the past for matching road vector data; however, these algorithms are not efficient enough for ad hoc integration. This article presents algorithms for ad hoc integration of maps in which roads are represented as polylines. The main novelty of these algorithms is in using only the locations of the endpoints of the polylines rather than trying to match whole lines. The efficiency of the algorithms is shown both analytically and experimentally. In particular, these algorithms do not require the existence of a spatial index, and they are more efficient than an alternative approach based on using a grid index. Extensive experiments using various maps of three different cities show that our approach to matching road networks is efficient and accurate (i.e., it provides high recall and precision).

General Terms:Algorithms, Experimentation     

Assessing similarity matching for possible integration of feature classifications of geospatial data from official and informal sources

One difficulty in integrating geospatial data sets from different sources is variation in feature classification and semantic content of the data. One step towards achieving beneficial semantic interoperability is to assess the semantic similarity among objects that are categorised within data sets. This article focuses on measuring semantic and structural similarities between categories of formal data, such as Ordnance Survey (OS) cartographic data, and volunteered geographic information (VGI), such as that sourced from OpenStreetMap (OSM), with the intention of assessing possible integration. The model involves ‘tokenisation’ to search for common roots of words, and the feature classifications have been modelled as an XML schema labelled rooted tree for hierarchical analysis. The semantic similarity was measured using the WordNet::Similarity package, while the structural similarities between sub-trees of the source and target schemas have also been considered. Along with dictionary and structural matching, the data type of the category itself is a comparison variable. The overall similarity is based on a weighted combination of these three measures. The results reveal that the use of a generic similarity matching system leads to poor agreement between the semantics of OS and OSM data sets. It is concluded that a more rigorous peer-to-peer assessment of VGI data, increasing numbers and transparency of contributors, the initiation of more programs of quality testing and the development of more directed ontologies can improve spatial data integration.     

整合异构地震数据库服务的新方法

整合异构地震数据库服务的新方法通过数据层采用透明网关技术实现异构数据库互连,应用层采取跨平台、跨语言的ICE中间件技术,实现并提供各种与业务相关的二次开发接口,用户通过该接口可以方便快捷操作业务数据;实验结果表明,该方法不仅屏蔽了异构数据库的服务差异,同时也大大提高了整合数据服务的效率.     

Nonlinear performance of classical damping

The performance of a classical damping matrix, constructed either from the use of initial structural properties or current structural properties, in the step-by-step solution of a nonlinear multiple degree of freedom (MDOF) system is analytically evaluated. The analytical results are confirmed by numerical examples. Consequently, some conclusions are drawn from these analytical results that might be considered as rough guidelines for practical applications. It is found that a classical damping matrix constructed from initial structural properties is adequate for practical applications, since it has approximately the same damping effect as obtained by current structural properties and is more efficient in terms of computing.     

An evaluation of ontology matching techniques on geospatial ontologies

Standardization is one of the pillars of interoperability. In this context, efforts promoted by the Open Geospatial Consortium, such as CityGML (Technical University, Berlin), a standard for exchanging three-dimensional models or urban city objects, are welcomed. However, information from other domains of interest (e.g. energy efficiency or building information modeling) is needed for tasks such as land planning, large-scale flooding analysis, or demand/supply energy simulations. CityGML allows extension in order to integrate information from other domains, but the development process is expensive because there is no way to perform it automatically. The discovery of correspondences between CityGML concepts and other domains concepts poses a significant challenge.

Ontology matching is the research field emerged from the Semantic Web to address automatic ontology integration. Using the ontology underlying CityGML and the ontologies which model other domains of interest, ontology matching would be able to find the correspondences that would permit the integration in a more automatic manner than it is done now.

In this paper, we evaluate if ontology matching techniques allow performing an automatic integration of geospatial information modeled from different viewpoints. In order to achieve this, an evaluation methodology was designed, and it was applied to the discovery of relationships between CityGML and ontologies coming from the building information modeling and Geospatial Semantic Web domains. The methodology and the results of the evaluation are presented. The best results have been achieved using string-based techniques, while matching systems give the worst precision and recall. Only in a few cases the values are over 50%, which shows the limitations when these techniques are applied to ontologies with a partial overlap.     

3D dynamic response of a transversely isotropic multilayered medium subjected to a moving load

The dynamic problem of a transversely isotropic multilayered medium is reducible to quasi‐static problem by introducing a moving system that travels synchronously with the load. Based on the governing equations in the moving system, the ordinary differential equations in the Fourier transformed domain are deduced. An extended precise integration method is adopted to solve the ordinary differential equations, and the solution in the physical domain is recovered by the inverse Fourier transform. Numerical examples are performed to verify the accuracy of the presented method and to analyze the influence of material properties and the load characteristic.     

Coupled three-dimensional discrete element-lattice Boltzmann methods for fluid-solid interaction with polyhedral particles

Interaction between solid particles and fluid is of fundamental interest to scientists and engineers in many different applications—cardiopulmonary flows, aircraft and automobile aerodynamics, and wind loading on buildings to name a few. In geomechanics, particle shape significantly affects both particle-particle and particle-fluid interaction. Herein, we present a generalized method for modeling the interaction of arbitrarily shaped polyhedral particles and particle assemblages with fluid using a coupled discrete element method (DEM) and lattice Boltzmann method (LBM) formulation. The coupling between DEM and LBM is achieved through a new algorithm based on a volume-fraction approach to consider three-dimensional convex polyhedral particles moving through fluid. The algorithm establishes the interaction using linear programming and simplex integration and is validated against experimental data. This approach to modeling the interaction between complex polyhedral particles and fluid is shown to be accurate for directly simulating hydrodynamic forces on the particles.     

空间数据访问集成与分布式空间数据源对象查询

目前,针对空间数据库的访问与处理方法,无法满足分布式环境下异构数据源的服务化存取和面向空间数据源的对象查询处理需求。本文给出了数据网格环境下的分布式空间数据访问与查询的方法和实现,并在服务化查询处理过程中,嵌入符合SQL/MM查询规范的空间拓展函数,实现分布式空间数据对象查询和嵌入查询过程中的空间数据分析处理。在此基础上,给出空间数据对象查询树的构造过程,以及分布式空间查询工作流的执行流程。数据访问与集成策略在空间数据处理上的应用,对异构空间数据源协同处理等,涉及大规模空间数据存取访问的应用需求,有很好的理论和实际应用价值。     

面向服务的地学多源数据虚拟整合及其可视化分析

科学数据共享的推进,给科研人员带来了前所未有的科研契机,但是依然没有摆脱"搜集数据-下载数据-整理分析数据"的科研流程,这种传统的科研流程已经严重阻碍了科研效率的产出,科研人员对信息和知识的需求已经远远大于对数据本身的需求,而要实现对信息和知识的挖掘,多源数据的实时整合与在线可视化分析是其关键。本文选择社会经济研究主题,以中国社会经济统计数据、国家基础地理行政区划矢量数据为例,并结合ESRI和Google的全球地图与影像服务,采用在线虚拟整合的方法,探讨了面向服务的地学多源数据集成方案及其可视化分析,以期达到快速的知识发现与信息获取。研究结果表明:面向服务的技术架构虽然已经成熟,相对于传统的数据共享和应用系统在数据接口开放性、集成性和应用扩展性等方面具有明显的优势,能够切实解决多源异构数据的整合问题,但是技术的成熟并不等于应用的成熟,广泛而成熟的应用不但需要技术的支撑,更需要友好和智能的操作界面,这方面还需要较长的时间去探索。从本文的应用实例来看,在面向服务技术的深入应用过程中,还存在着不同来源数据单位不统一、操作流程复杂、服务规范不统一等问题。同时,在不同类型服务的标准化、操作智能化和多源服务的功能应用模块化等方面还需要大量的实践,才能进一步推进地学信息化科研环境的建设,以全方位为科研人员服务。