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The visualization of flood disasters in virtual reality (VR) scenes is useful for the representation and sharing of disaster knowledge and can effectively improve users’ cognitive efficiency in com...

Flood visualization is an effective and intuitive tool for representing flood information from abstract spatiotemporal data. With the growing demand for flood disaster visualizations and mitigation...

The complexity of interrelationships between urban natural environments and human environments is increasing with rapid urbanization. This brings new challenges to urban modeling and simulation in simultaneously meeting the comprehensive needs of the dual integration of data and models, multi-type visualizations, human-centered simulation, geographic collaboration, and interactions between physical and virtual spaces. We here propose virtual geographic environments (VGEs) as a new platform of urban modeling and simulation. After discussing the evolution, definition, and features of VGEs, we design a VGE framework for urban system modeling and simulation. Two typical cases are provided to illustrate how VGEs support urban modeling and simulation on different scales: VGE-based collaborative modeling and the simulation of air pollution dispersion in the Pearl River Delta (PRD) urban agglomeration, and fire emergency crowd evacuation simulation. In the future, VGEs may also play an important role in digital twin cities and urban metaverses.

Disaster scene symbols can reduce memory and cognitive burdens and improve the transmission efficiency of debris flow information. There is no unified standard for disaster scene symbols, although many academic institutions and emergency departments have thoroughly studied debris flow disasters. Instead, many disaster scene symbols of different styles interfere with the public's understanding of disaster information. Here, an optimal selection method for debris flow scene symbols considering public cognition differences is proposed. First, public knowledge is incorporated into the fuzzy analytic hierarchy process (FAHP) model for debris flow scene symbol selection. Second, debris flows are visualized in 3D with a virtual geographic environment (VGE). Finally, a real debris flow is selected for experimental analysis. The proposed method can support the optimal selection of debris flow scene symbols considering public cognition differences, and a 3D scene constructed with the selected symbols can improve the transmission efficiency of disaster information and provide support for public-oriented debris flow information services.

Large-scale crowd evacuation simulation in virtual reality is of great significance for emergency response. However, the existing large-scale crowd evacuation simulation methods are challenging to apply to the virtual reality scene. Thus, the efficiency of large-scale crowd rendering in virtual reality needs to be improved. Here we proposed a chain navigation grid for virtual reality large-scale crowd evacuation simulation. The objective of this study was to apply traditional cellular automata crowd evacuation simulation algorithms to virtual reality scenes through a chain navigation grid. Combined with the characteristics of crowd movement, we proposed the vertex raster rendering method to efficiently visualize large-scale crowds in virtual reality scenes. Finally, we constructed two evacuation scenes and carried out experimental analyses. The results show that the chain evacuation navigation grid can transform the discrete crowd movement of cellular automata into continuous crowd movement in virtual reality and can connect multiple cellular automata corresponding to multi-floors. Compared with the evacuation results of Pathfinder software, the chain evacuation navigation can add the factor of environmental familiarity. Therefore, this study improved evacuation simulation by increasing about 6% efficiency in time and computing process. Compared with the traditional crowd evacuation rendering method, the vertex raster rendering method increases the maximum number of people rendering from 2 times to 31 times.

Scientific and appropriate visualizations increase the effectiveness and readability of disaster information. However, existing fusion visualization methods for disaster scenes have some deficiencies, such as the low efficiency of scene visualization and difficulties with disaster information recognition and sharing. In this paper, a fusion visualization method for disaster information, based on self-explanatory symbols and photorealistic scene cooperation, was proposed. The self-explanatory symbol and photorealistic scene cooperation method, the construction of spatial semantic rules, and fusion visualization with spatial semantic constraints were discussed in detail. Finally, a debris flow disaster was selected for experimental analysis. The experimental results show that the proposed method can effectively realize the fusion visualization of disaster information, effectively express disaster information, maintain high-efficiency visualization, and provide decision-making information support to users involved in the disaster process.

Evacuation simulations in virtual indoor fire scenes hold great significance for public safety. However, existing evacuation simulation methods are inefficient and provide poor visualized when applied to virtual reality (VR) simulations. Additionally, the influences of the interaction of evacuation processes on the choice of multiple exits have not been fully considered. In the paper, we propose a VR simulation method for crowd evacuation in a multiexit indoor fire environment. An indoor 3D scene model and character model, for studying the environmental factors that affect the multiexit selection of personnel during the fire process, are combined with environmental factors to enhance the evacuation route planning algorithm to improve the efficiency of the VR simulation of evacuation in the scene. In addition, a prototype system that supports multiple experience modes is proposed, and case experiment analyses are performed. The results show that the method described in this paper can effectively support the real-time simulation of indoor fire evacuations in virtual scenes, providing both reliable simulation results and good visualization effects.

The dynamic deformation of virtual terrain is an important research content to improve the dynamic adaptability of virtual geographic environment, which can support the research of disaster simulation, combat simulation and so on. It is also a novel method to support human-environment interaction research in the community of geographic information science. In this paper, the dynamic generation of bomb crater is taken as an example to study the construction method of virtual terrain deformation model. Starting from the formation process of crater in explosive mechanics, the deformation model is coupled with the calculation method to control the radius and depth of crater shape. Through the method of geometric fitting, the shape of crater is modeled in different regions and the basic crater model is established. On the basis of the basic model, the incidence angle of projectile is introduced to build the relationship model between crater deformation and incidence angle of projectile. Based on the Digital Terrain Model (DTM), the terrain data model is improved by coupling the radius coefficient and depth coefficient related to the geological characteristics, and the crater shape algorithm reflecting the geological characteristics is proposed. Finally, the Perlin noise is added to realize the disturbance of the elevation value of each position point in the crater zone. The simulation environment of crater deformation is established by Unity, and the crater model is simulated and verified. The results show that the crater model can basically reflect the impact of different projectile incidence angle, explosion equivalent and geological characteristics. The deformation state of crater is similar to the actual situation. The research results can provide support for the simulation of the dynamic process of the crater produced by the projectile touch-down explosion in the virtual battlefield environment.

article i nfo Virtual Geographic Environments (VGEs) are proposed as a new generation of geographic analysis tool to contrib- ute to human understanding of the geographic world and assist in solving geographic problems at a deeper level. The development of VGEs is focused on meeting the three scientific requirements of Geographic Information Sci- ence (GIScience) — multi-dimensional visualization, dynamic phenomenon simulation, and public participation. To provide a clearer image that improves user understanding of VGEs and to contribute to future scientific devel- opment, this article reviews several aspects of VGEs. First, the evolutionary process from maps to previous GISystems and then to VGEs is illustrated, with a particular focus on the reasons VGEs were created. Then, extend- ed from the conceptual framework and the components of a complete VGE, three use cases are identified that together encompass the current state of VGEs at different application levels: 1) a tool for geo-object-based multi-dimensional spatial analysis and multi-channel interaction, 2) a platform for geo-process-based simulation of dynamic geographic phenomena, and 3) a workspace for multi-participant-based collaborative geographic experiments. Based on the above analysis, the differences between VGEs and other similar platforms are discussed to draw their clear boundaries. Finally, a short summary of the limitations of current VGEs is given, and future directions are proposed to facilitate ongoing progress toward forming a comprehensive version of VGEs.

Air pollution, which is a global environmental problem, has been the hot research area among the scientists in the geoscience community. Air pollution simulation is of low-efficiency caused by the computation-intensive models, such as MM5 or WRF, and the complicated and unfriendly user interface. These issues are addressed in this paper by integrating computational grid and virtual geographic environment (VGE). The computational grid is employed to improve the computation efficiency of air pollution models. The VGE is used as a straightforward and easy to use interface to navigate the air pollution modeling workflow and improve the operational efficiencies of the models with respect to initiation, computation, and output visualization. On the aspect of technique implementation, this paper designs a framework and addresses the methodologies of the integration of computational grid and VGE. The prototype system, which integrates the computation grid of the Chinese University of Hong Kong (CUGrid) and a VGE to facilitate air pollution simulation based on the Mesoscale Model Version 5 (MM5), was developed. Based on the prototype system, a case was tested and the results indicate that the efficiencies of air pollution simulation on the model computation and workflow operation based on MM5 are increased significantly. This success also proves the reasonability of our general contribution of integrating computational grid and VGE to facilitate air pollution simulation.

The integration of high dimensional geo-visualization, geo-data management, geo-process modeling and computation, geospatial analysis, and geo-collaboration is a trend in GIScience. The technical platform that matches the trend forms a new framework unlike that of GIS and is conceptualized in this paper as a collaborative virtual geographic environment (CVGE). This paper focuses on two key issues. One is scientific research on CVGE including the concept definition and the conceptual and system framework development. The other is a prototype system development according to CVGE frameworks for air pollution simulation in the Pearl River Delta. The prototype system integrates air pollution source data, air pollution dispersion models, air pollution distribution/dispersion visualization in geographically referenced environments, geospatial analysis, and geo-collaboration. Using the prototype system, participants from geographically distributed locations can join in the shared virtual geographic environment to conduct collaborative simulation of air pollution dispersion. The collaborations supporting this simulation happen on air pollution source editing, air pollution dispersion modeling, geo-visualization of the output of the modeling, and geo-analysis.

This paper aims to design and develop a Distributed Virtual Geographic Environment (DVGE) system. A DVGE system is an Internet-based virtual 2D and 3D environment that provides users with a shared space and a collaborative platform for publishing multidimensional geo-data, and for simulating and analyzing complex geo-phenomena. Users logging into the system from different clients can share distributed geo-information resources, including geo-data and geo-models, and can complete collaborative tasks. Web service technology provides effective solutions for constructing DVGE systems because of its ability to support multi-platform, multi-architecture, and multi-program-language interoperability on the Internet, but also because of its ability to share programs, data, and software. This paper analyzes the characteristics, relevant technologies, and specifications of web services, such as grid services, Open Geo-data Interoperability Specifications (OpenGIS), and Geography Markup Languages (GML). The architecture and working mechanisms of the DVGE system based on web services are then elaborated. To demonstrate DVGE systems based on web services, we examine a case study of water pollution in Yangzhou City, Jiangsu Province, China, using a prototype DVGE system that is developed with Jbuilder9.0 and Java3D 1.0 packages, and the Weblogic platform 8.1.

In this paper, we explicitly propose the problem of Frequency Hopping (FH) signal acquisition, and analysis the different algorithm to estimate the frequency of FH signal. We develop a sophisticated algorithm which combines the adaptive Pisarenko's Harmonic Deposition(PHD) and the modified least-square-lattice(LSL) algorithm. So the convergence rate of this algorithm has been further increased and convergent property of the adaptive implementation of PHD has been improved. Simulating results further verify the correctness and accuracy of the algorithm.

Geographic information system (GIS) professionals recognize that geographic process is essential for understanding what is happening in the world, learning how the environment is changing, modelling how complex systems work and giving context to other types of data. Consequently, geographic process models have been increasingly featured for the next generation geographic information science (system), as a method for phenomena simulation and mechanism analysis of the physical environment and its live activities, thereby driving conventional GIS based on data manipulation into the world of dynamic and computational processes (Goodchild, 2006; Yuan and Hornsby, 2008; Torrens, 2009; CSDGS et al., 2010).

A real-time virtual geographic environment (VGE) can serve as interactive, intuitive visualization tools for exploring, analyzing, synthesizing, and simulating multi dimension geo-data and complex geo-phenomena. The VGE scene can be constructed by terrain models, building models, and natural gaseous phenomena models. This paper used a viewdependent simplification method to improve the rendering efficiency of the VGE scene. The continuous level of detail technique(C-LOD) algorithm was adopted to achieve high frame rates by generating an approximate view-dependent triangulation of large terrain scene. Meanwhile image-based rendering techniques such as the imposter billboard were used to speed up the visualization of 3D object models (e.g., 3D building, 3D trees, smoke, cloud and so on). Using the Pearl River Delta (PRD) region in China as a case area, the visualization environment was built to support real-time rendering of larger-scale geo-scene. Experiment results prove that the scheme addressed in the paper can improve the overall efficiency.

Virtual Geographic Environment (VGE) is a virtual representation of the physical world, culture world and imaginary world. Compared with GIS, VGE has two core components, which are Data and Model respectively. Many models in VGE are complex and therefore the model calculations for them are very time consuming as well. How to decrease and reduce the required model computation time to improve VGE efficiency will be a vital and key issue for most of the VGE implementation. In this research, we adopt CUGrid as the model computation server, which contains more than two hundred CPUs for fast and intensive computation. With the CUGrid, MM5 based air pollution data in Pearl River Delta is used as the test case for this study. According to the test results, we managed to reduce the required model computation time from the original three months on one specific desktop to several minutes on the CUGrid. Another significance and benefit of this research is that we also able to integrate MM5 with geographic information, which makes concepts on air pollution can easily be understood by the public.

The rapid economic development of the PRD (Pearl River delta) has led to severe air pollution. Air pollution control is critical for sustainable development. From a geographic viewpoint, this paper will focus on how to develop a virtual geographic environment (VGE) to study environmental issues. Unlike existing work, our methods pay attention to dynamic 3D volume representation in virtual PRD terrain environment, which make air pollution transportation and dispersion easily understood to public and officers. Moreover, some GIS spatial analysis and real-time interactive operation with VGE will also be implemented to support the management and control of atmospheric pollution. A prototype system is developed to construct a virtual geographic environment for simulating the PRD region air pollution and dynamic interaction. Experimental results prove that the scheme addressed in the paper is effective and feasible.

A geographic information services grid (GISG) is an open frame and software system based on grid for discovering, sharing, processing, integrating multi-source and heterogeneous geographic information, and conducting collaborative work. At present, many technologies are introduced and applied to implement sharing, integration and collaboration of geographic information, of which grid computing technology, OpenGIS, and Web services are the most important ones. In this paper, we aim to utilize Open GIS specification and Web services technology to design the architecture of GISG according to OGSA. Specially, GI services are taken as the GISG's center. Based on GISG, we develop designa framework for establish the public health management and disease control system.

As a development in geography and geographic information science, virtual geographic environment (VGE) embodies abstract concepts, makes people immerge in the virtual world, studies the geography problems, and carries out geographic examinations. VGE has plenty of multi-kinds of data, such as digital elevation model data, data of objects under and on the Earth surface, image data, audio data, video data, avatar movement data, interaction data, environment data, and so on. VGE data can be classified as dynamic data and static data according to data changing. At the same time, VGE data can also be classified into global data and local data with an eye to data using range. According to VGE data attributes and its classifications, we design a VGE database, which fits VGE's three main contents: virtual geographic environment construction, entities construction and the interaction between environment and entities. There has a global database to store global data and several local databases to store their region data. The database is also distributed, so we study a method and an architecture to solve the database collaboration. We call the method "pre-data-preparing". In the end, we give an example of DEM database collaboration of GuanTing lake located in the west of Beijing.

Data visualization is an important technique that helps in understanding and analysis of complex data. Geo-spatial data is quite different from other kinds of data, for its unique properties of territorial, multidimensional structural and dynamic change. VR technologies have considerable potential to extend the power of geo-spatial data visualization methods which traditional GIS can not provide. Although Virtual GIS can provide the functions of the 3D-visualization analysis for spatial data, these systems are dependent upon specific platforms and programming languages without interoperability. Web services are very suitable for solving above problems. In this paper, we design and implement a spatial data 3D-Visualization web services for publishing multi-dimension geo-data in order to make independent GIS software share distributed geo-information resources including geospatial data and 3D-visualization geo-model, and realize them interoperability. The web services are used to construct the land view with DEM data and remote sensing data based on Java3D, and are deployed in Weblogic8.1 server and published in IBM UDDI registry center on Internet. At last, a client of the web services is created to test the effect of the spatial data 3D-Visualization web services.

Flood disaster loss evaluation (FDLE) plays a very important role in Flood Control Decision Support System (FCDSS). In recent years, there are more and more spatial data, especially Remote Sensing (RS) images data. Meantime, the updating ratio of RS images data is faster too. So in this paper we focus on flood disaster loss evaluation model based on RS images. It is very difficult to get value information in real time because all RS data resources are geographically distributed and heterogeneous, and these data update is also not rapid through traditional data service mode such as data purchase. Grid technology can provide us the capability to solve these issues effectively. In this paper, we firstly address the major characteristics of RS and Grid technologies, and analyze the possibility for FDLE services. Based on Grid technology, then we design the FDLE service system architecture and its implementing mechanism is addressed. Meantime, some key technologies such as data management and services management also are discussed. Finally, we implement an application service. All these efforts will help us integrate all diverse and separated data resources and offer more convenient and rapid FDLE information services. The experiment result shows that the scheme addressed in the paper is efficient and feasible.

Virtual Geography Environment (VGE) is a comprehensive subject concerning remote sensing, geography, information theory and communication etc. There have multi-source, diff-structure, interdiscipline, and inter-organizations data related to VGE. Moreover, the tasks in VGE will cover many aspects inevitably. In order to complete the task proposed by user, it is required to integrate, link and share the distributed data in different organizations or domains. But it is almost impossible to solve many problems by using traditional ways such as changing some kinds of data structures which has formed standard. The advent of the third network technology, Grid, gives VGE new dimension of development. Grid has some hard core functions, such as shielding diff-structure data, harmonizing resource-sharing and cooperating with each other in virtual organization to complete the task. Based on the Grid and VGE, the Grid Virtual Geographical Environment (Grid-VGE) is put forward, which abides by the standard of Open Grid Services Architecture (OGSA), takes Services as core and constructing virtual database. In order to link, integrate and share all required data, we abstract all data into metadata and description to interlink through link based on the standard of OGSA. The proposed data structure method can absorb any data anytime while not modifying the original data and it will enlarge and increase efficiency of the application in VGE.