Research on Three-dimensional Integrated Visualization Architecture Based on Virtual Globe and Service-Oriented Architecture

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1 Research on Three-dimensional Integrated Visualization Architecture Based on Virtual Globe and Service-Oriented Architecture 1,2 Wang Xianghong, 2 Liu Jiping, 2 Xu Shenghua, 2 Wang Yong *1 School of Geomatics, Liaoning Technical University, xhwang0828@gmail.com 2 Chinese Academy of Surveying and Mapping, {liujp, xushh, wangyong}@casm.ac.cn Abstract For the sharing integration and 3D visualization of multi-source, heterogeneous, widespread distribution information, we propose a three-dimensional integrative visualization architecture based on SOA and virtual globe. The paper elaborates on the overall architecture and the relative fundamental technologies. Then studies the key technologies, such as the unified 3D integration of 2D GIServices (geographic information service) and 3D GIServices based on sphere model, the service resource management, and 3D integrated visualization expression. Finally, we select several typical services to demonstrate the 3D integrative visualization architecture, and achieve 3D integrative visualization of GIServices, thematic data services and business applications in virtual globe. The practical application shows that the proposed architecture is feasible, reliable, practical and efficient, and using the virtual globe is a wonderful solution to share, integrate and express the web services. Keywords: Service-Oriented Architecture, Virtual Globe, Three-Dimensional Integrated Visualization Architecture, Service Management, Service-Based Integration, Three-Dimensional Visualization 1. Introduction With the rapid development of computer technology and Earth observing technology, the development and application of GIS has been accelerated. GIS has been widely used in resource management, environmental monitoring, transportation, urban planning, economic construction, as well as various government departments [1], and achieved good economic and social benefits. Along with the depth of the process of informatization in various departments, GIS has become the basic platform for integrating the thematic data with the spatial data. Owing to the lack of a unified of system planning, architecture, software technical standards, etc., resulting in the so-called "information silo" [2], and it s difficult to integrate a variety of data which has these features such as multi-sources, multi-types, multi-formats, heterogeneous and widespread distribution. The traditional GIS systems lack of effectively approach of information sharing, its framework and model is more difficult to flexible implement the multi-level integration of geographic information services and applications. Therefore, it is crucial to provide integrative visualization architecture so as to be able to efficiently and effectively promote the integration and sharing of data, information resources and applications among departments. SOA can provide a reliable environment for information integration and sharing. With the improvement of the SOA ideas and the implementation of the technology matures, SOA has been extensively and intensively applied in GIS domain, and propose a new software mode to sharing integration and interoperability of distributed, heterogeneous data [3], and also provide technology accumulation for the development of Cloud GIS. Spatial information visualization is used for further exploration of spatial information through the visual effect in a virtual geographical environment. Currently, Digital Earth with its intuitive and real display effect, favored by the majority of users. It s possible to establish a unified digital earth platform, along with relative technologies and OGC standards continue to improve. However, an efficient integration architecture and method based on digital earth platform to integrate the distributed resources is still far from being achieved. Moreover, research on 3D GIServices, data integration, information fusion and others based on virtual globe is also lagging behind [4-6]. This paper analysis and summarize some typical GIS integrative and visualization technology, especially in information sharing, data fusion and 3D visualization technology. To address these problems, the present study designs a three-dimensional integrative visualization architecture based on virtual globe and SOA, and then elaborates on the key technologies in detail, such as the approach of Advances in information Sciences and Service Sciences(AISS) Volume5, Number6, March 2013 doi: /aiss.vol5.issue

2 service integration and 3D visualization, service resource management and others. Finally, a prototype system is developed to demonstrate the architecture and these technologies. 2. Related Works SOA is a software system construction method which provides services to applications and other software systems on the network by the service interfaces that has published and can be found. The core of SOA is that combines the business functions in different levels by the way of loosely coupled to achieve the business agile [7]. It enables sharing of resource through the Web services. Scholars at home and abroad have carried out the extensive research on GIS theory and applications based on SOA, and have obtained some achievements. Li Deren et al establishes an SOA-based model of spatial data sharing and geospatial information sharing platform, and validation with multi-source spatial information sharing platform in the city [8]. Wu Xincai proposes a Web services and spatial information technology integration mechanism, and established a service-oriented distributed spatial information support platform [9]. Chi Wenxue et al proposes an SOA-based GIS data integration methods, it realizes geographic information data share and interoperability among the different corporation, different platform and different data structure, and then using Web Services technology to integrate heterogeneous data [10]. Martin Treiblmayr et al presents and discusses a service-oriented architecture that embraces a GIS and an enterprise resource planning system, it analyzes essential ontological distinctions for mapping conceptual schemes in GI locator services and non-gi services [11]. Additionally, many scholars and technicians have conducted in-depth research from the integration architecture, service registration, service management, service discovery, service aggregation, and interoperability and so on, laid the technical foundation for further application of SOA in GIS [12-17]. The rapid development of virtual earth technology has been applied in many fields, such as digital city, emergency response, urban planning and design, intelligent transportation, virtual tourism, etc. With the development of computer network technology, web-based 3D geographic information system has become a hotspot of research and application. Three-dimensional web-mapping viewers using a virtual globe to portray the world have helped to popularize GIS, transforming a flat 2D world into a more stimulating experience for the general public. Gong Jianya et al explores the theory, method and key techniques of management, network transportation, sharing integration and visualization of the multi-source, multi-scale, multi-date mass geoinfomation in online three dimension virtual globes. As the basis for it, the open-type of virtual globe sharing integration platform is developed, and successfully implicated in a serious item such as National geographical information of public service platform [18][19]. Google Earth, Microsoft Virtual Earth, NASA World Wind, SkylineGlobe, ESRI ArcGIS Explorer and EV-Globe are well-known digital earth platform. Based on these mature 3D platforms, they have carried out some researches and applications such as 3D integration of thematic data [20-22]. Geographic information web services is an application of Web services technology in the field of GIS, refers to Internet applications which use the data and related functions to complete basic geosciences processing tasks [23]. With the increasing requirements of digital earth, building 3D geographic information service based on the digital earth platform has become one of the main interests of spatial information service fields. 3D GIService can provide a sense of real terrain, flexible and interactive 3D data services and 3D spatial analysis services based on remote sensing images, DEM, 3D model, and all kinds of vector data. It s used to build by OGC Web services standards and specifications, such as WFS, WPS, WCS, W3DS, WVS, etc. Research on data integration and application based on the 2D GIS platform by web services is relatively mature [24][25], but integration of 2D/3D GIServices based on the digital earth platform is started later. Most of the works done by the previous scholars have tried in SOA-based GIS application, services publishing and management, geospatial data sharing integration based on 2D GIS and so on, research on integrating 2D/3D GIServices, thematic data and analysis functions based on virtual globe is relatively less. This paper summaries and analysis of research and application of existing SOA in the field of GIS, on the basis of this review, the study designs a 3D integrated visualization service framework based on virtual globes and SOA, it not only enables web-based unified management the distributed and multi-type of service resource, and can also realizes integration and visualization of 2D/3D GIServices, thematic services and analysis services in the virtual globe. 450

3 3. Three-dimensional Integrated Visualization Service Framework 3.1. Web services architecture Web services architecture is a message processing framework, using a series of standards and protocols to ensure that the message is unified communications, addressing and transmission, and has the characteristics of cross-platform, loosely coupled, reusable, and easy extension. Figure 1 illustrates the basic Web services architecture, in which a service requestor and service provider interact based on the service's description information published by the provider and discovered by the requester through some form of discovery agency [26]. Service requesters and providers interact by exchanging messages. Figure 1. Components, Roles and Operations in Web Services Architecture In the diagram above, the nodes of the triangle represent roles and the edges represent operations. Interaction among different roles is achieved by three basic operations (publish, find and interact). Service provider: The provider provides web services which satisfy the contract and implemented by an appropriate agent, these services will be published in service registration center in accordance with the registration mechanism, and response to service requests. Service requestor: That s the service consumers, it can search the description of service from the registration center by using the Find operation, and then bind the service provider and call the web service to achieve the corresponding functions. Service registration center: It provides registration and search functions, and manages the registered web services Overall architecture Reference to the ideas of SOA, and think of the integrated application requirements for the distributed multi-source, heterogeneous data and application system, we designs a sharing integration visualization service framework based on SOA and virtual globe, as shown in Figure 2. It has four layers logically: application layer, business logic layer, service layer and data layer. Application layer: this layer is the service consumer, and also is the carrier of the 3D scene rendering and display. It can communicate with the service layer or the service registration center to find the necessary services, and can display services on a desktop view or a normal browser. Business logic Layer: it s a link between the service layer and the application layer, and mainly builds a service registration center based on UDDI, to register and manage services. Moreover, using multi-agent, multi-threading technology and service object management based on service pool [27][28], to improve the efficiency of the service response. Service requester binds web services through WSDL interfaces dynamically, and then achieves network-based data transmission and interaction. Service Layer: its function is a bridge between the application layer and the data layer. It mainly includes 2D GIServices, 3D GIServices, business services, and data access interface. 2D GIServices is the traditional GIS data service which is compatible with this architecture; 3D GIServices contains services such as terrain, place name, model, feature and other services; business services mainly refer to functional prototypes to support business applications; and the interface interacts with the data layer, extract the appropriate data according to the service parameters. Data layer: it mainly includes all kinds of GIS data and thematic data which are stored in databases, files, etc., and other data or service is provided by applying system. The layer uses the unified data 451

4 organization, storage and access mechanism for 2D data and 3D data, so it s not necessary to distinguish between 2D data and 3D data, only need to manage the corresponding relationship of the services and data. This study uses the combination of catalog and metadata to manage those resources. Figure 2. Integrative visualization architecture 4. Key Technologies of Three-dimensional Integrated Visualization 4.1. Methods of three-dimensional integrated visualization The three-dimensional virtual scene can compensate for the lack of expression of the 2D GIS, and make the visual effect more intuitive, vivid, and imagery. This proposed architecture supports the resources integration loosely coupled. It takes into account the characteristics of the web services and the specified display requirement, and achieves the integration of data, services and functions. This section will discuss some key issues for unified 3D integration of 2D GIServices and 3D GIServices Spatial reference unified mechanism Uniform spatial reference is the prerequisite of integration, that is, the data which is displayed in the same frame must have the same spatial reference, otherwise cannot display correctly. In this paper, the 3D virtual scene takes the geographic coordinate system based on the WGS84 ellipsoid as the spatial reference datum. The different spatial reference service needs to convert coordinate system and projection. The framework supports two ways of processing. One is that the data are transmitted to the WCTS services, which support the conversion of a variety of geospatial reference systems, to achieve coordinate conversion in server-side. The other is directly processed in the 3D client - side of the relative functional modules. This virtual globe also supports the Web Mercator projection Three-dimensional visualization of 2D GIServices There are two levels of 2D GIServices, the graphic level and the data level. Service of graphic level is used to virtual expression and provides users with intuitive visual result, which is established by OGC standard services, such as WMS, TMS, WTMS, WCS and W3DS and so on, and returns the result with the image. Generally, some analysis function uses this service, such as seismic intensity analysis. Service of data level is established by OGC WFS, user-defined service and other services, it returns the result with the format such as XML, GML, KML, and binary stream and so on. For example, 452

5 place names and POI use this way to provide services. Combing with these two levels of services not only makes data visualization qualitatively, but also can analyze the data quantitatively. The service of graphic level is visualized the methods of overlay, adding image layers, etc. Threedimensional visualization of 2D GIS services is primarily for the service of data level, this type of service return data itself to the client, the 3D Client will dynamically generate 3D rendering object, such as points, lines, polygons, and 3D models and so on, according to the coordinate and attribute information, and finally achieve three-dimensional visual expression of 2D GIServices Three-dimensional web service resource management This integrative visualization architecture contains the services can be divided into the following several categories respectively: registration service, data service (2D GIServices, 3D GIServices, thematic data service, etc.), processing service, functional service, and system management service. The service framework makes unified management of the registered service resources, and defines the XML-based service description document which is used to describe the registered service and its instance; the document mainly includes service name, service provider, service type, service address and other relevant information. It realizes unified code of metadata information on the registered service. Figure 3 shows the description document about an image data service. Additionally, this paper studies the description of various types of services from registration management, obtaining and parsing, as well as calling and test. The service description document ensures that all kinds of services can be found and aggregation quickly. Figure 3. Service description information in XML format The service description can be published to the service registration center. All web services clients can use the initiative search tool, which use the key word, data attribute and functional property, to find the service description, and then use the service description to bind the service provider and invoke the service. Figure 4 shows the registered description information in the service registration center. 5. Applications Figure 4. Overview of the registration of service in the service registration center In this paper, three types of services are selected particularly as the experimental web services: fundamental geospatial data service, POI thematic data service, and typical analysis service. Following the integration mechanism, the integrative framework uses the virtual globe to integrate and visualize those services, and verify its credibility, reliability and efficiency. 453

6 5.1. Integration of fundamental geospatial data services The proposed virtual globe can integrate and visualize many kinds of fundamental geospatial data, such as remote sensing image, DEM, place names, vector data and 3D model and so on. These data are usually published following OGC specifications, and the services are registered in the service registration center. According to the configuration information of the loaded layer, the 3D client sends the request to the web server layer, which will parse these request parameters and find the corresponding agent. The agent calls the specified service by analyzing the request parameters, and then returns the results to the client for display. Figure 5 shows the 3D visualization of geospatial data services. This architecture can easily integrate represents the multi-source, heterogeneous geographic data from 2D/3D geospatial data services. Figure 5. 3D integrated visualization of geospatial data services 5.2. Integration of thematic data services The rules of thematic data services among the different department are inconsistent. Hence, we must take some operations before integration which makes the services has the same spatial reference, such as coordinate transformation, projection transformation, and spatial data model transformation and other operations. a) b) Figure 6. a): Thematic data registration interface window, b): 3D integrated visualization of reservoir information service This paper selects the reservoir data as the experimental data. Firstly, the user need to register the data, the registration interface window as shown in Figure 6 a), meantime, using the conversion tool to transform the spatial reference in server-side if necessary. And then following the registration wizard to configure the related fields and associate the attribute information. At last, the client can invoke and integrated visualize these data by the system-defined data services. Figure 6 b) shows the 3D 454

7 integrative visualization of the multimedia information on reservoir. The virtual globe also supports the thematic data query, location, statistical analysis and other functions Integration of analysis services There are mainly two ways for 3D integration of analysis services. One method is that the 3D client integrates with the result images which are generated by the analysis in server-side. Another is the server-side sends the result data itself as the format of XML, GML, and KML and so on, to the client, and then visualizes it. Figure 7 a) shows the 3D visualization result of seismic intensity analysis service, which are implemented by the overlay function [29]. The 3D integrated visualization result of contour analysis service is shown as Figure 7 b). For this type of services, the virtual globe uses the lines to represent the value of contour, and can set the style of line, such as color, line width, etc. In addition, the client uses some technologies to enhance the efficiency of the 3D rendering, for example, LOD, multi-threading, view frustum culling and so on. a) b) Figure 7. a): 3D integration of seismic intensity analysis service, b): 3D integrated visualization contour generation service 6. Conclusion Service-oriented architecture for building software is not new itself and has been proved to be an effective structure in implementing software applications [30]. It provides a unified basic technical framework which aims at obtaining, processing and application of spatial information, and also provides intelligent spatial information processing platform and basic application environment. This paper presents fundamental techniques for three-dimensional integrative visualization of spatial data, non-spatial data and some business applications. Based on this review, we design a 3D sharing integrated visualization architecture based on SOA and virtual earth platform, and elaborate on it in detail. The paper focus on these key technologies, such as 3D GIS web services, the unified integrated 3D visualization method of the 2D services and the 3D services, and registered service resource management, to achieve the integration, aggregation, sharing and visualization of the service. Finally, we select several typical services to illustrate this architecture using a virtual earth prototype system, and effectively demonstrate the method and architecture. This study is a valuable practice of the three-dimensional integrated visualization based on virtual globe, and can provide technical support for the construction of a sphere-based thematic data integration system. 7. Acknowledgements The authors gratefully acknowledge the discussion with Dr. Xu S. H. of Chinese Academy of Surveying & Mapping, and thanks to the classmates in our laboratory for their help. The study supported by the National Natural Science Foundation Grant # , the National High Technology Research and Development Program of China (863 Program) (Nos. 2012AA12A402, 2012AA12A309), and the National Science & Technology Pillar Program (Nos. 2012BAB16B01, 2012BAH28B03). 455

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