Virtual Geographic Environment Research Articles

Research on Spatial Cognition Training Based on the Digital Earth

Spatial Cognition ability reflects the level of real-time spatial orientation and situation awareness of pilots during flight, which is one of important factors that determines the level of flight ability. This paper explains the Spatial Cognition principle and training methods, and researches training methods of Spatial Cognition based on the 3D virtual geographic environment of Digital Earth, striving to break through bottleneck of the traditional Spatial Cognition training methods.

Preliminary Study on Voxel-Based Virtual Geographic Environment Representation

The expression of virtual geographic environment is based on the surface modeling, such as three-dimensional terrain modeling and rendering most of which are based on the polygon grid and 2D textured. In the expression of extreme terrain, such as caves, cliffs, canyons it seems powerless. However, the voxel-based terrain modeling has been more useful than polygon modeling expression in the field of real-time terrain deformation, extreme terrain simulation and geographic process expression. Furthermore, virtual geographic environment based on the traditional surface model is difficult to realistically simulate the real world which is volumetric. This paper analyzes the trends of the geographical environment representation, and discusses the typical voxel-based applications in natural phenomena simulation, terrain modeling and spatial process analysis. It provides the references for the integrative representation of the unified voxel and surface model, and for the construction of virtual geographic environment unified platform.

Integration of a computational grid and virtual geographic environment to facilitate air pollution simulation

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 Fast Modeling Service of Virtual High-speed Railway Scene

The high-speed railway technology has been growing rapidly in China. At the end of December 2012,the mileage of the high-speed railway in China had been nearly 9356 kilometers. China has become the country which has the scale biggest of high-speed railway mileage in the world. Simulation of general coupling system of high-speed railway is a highly complex dynamic process. Different domain objects have complex and dynamic relations, which are uncertainty and randomness. Thus, it is very important that these simulation data are implemented analysis, reorganization and visualization in a virtual geographical environment. Based on the special spatial features and the relationship attributes of high speed railway environment, this paper proposed a modeling method to meet the higher requirements of the visualization and management of high-speed railways. Some key problems including the creating of the primitive model base, the design of the ontology knowledge base and spatial semantic constraint rules were addressed in detail to develop a modeling service system and related plug-ins, which can provide fast modeling service for virtual high speed railway. Finally, a prototype system was implemented for modeling experiments on a case study region. The experimental results show that the proposed method in this paper can efficiently clarify various relations of scenes object entities, separate the domain knowledge from the modeling operation, and reduce the complexity and difficulty of the multidisciplinary collaborative modeling. It can support fast organization and modeling of virtual high-speed railway scene.

A New Synchronous Visualization System for Time-sequential 3D Geographical Scene Display on a Computer with Multiple Screens

Three-dimensional(3D) visualization of geographical scene is an important technique in Virtual Geographical Environment(VGE) research for a broad variety of complex natural phenomena and geographical processes.Because geographical scenes are in general highly complex,large scale and with strong interactivity features,traditional single computer single-screen display method usually fails to meet the application requirements of user immersion,large field of view,and high-resolution visualization.Multi-screen display technique is an effective way to solve this problem.In the human-computer interaction of 3D geographical scenes visualization,in addition to supporting to control by hand through the input of keyboard,the system also supports automatically roaming along the path designed in advance.The path for automatically roaming is generated by Cardinal interpolation method which have some advantages: setting simply,good shape retention,and roaming smoothly.In this paper,a new synchronous visualization technique and system for time-sequential 3D geographical scenes displaying and roaming is introduced.The system is based on a stand-alone computer with multi-screens,using vegetation cover changes prior to,during and after the soil erosion control in Changting County,Fujian Province as an example.The software architecture,implementation techniques such as scene construction with three viewports,synchronous display and synchronous route roaming with three screens,vector layer symbolization,embedded broadcasting real-world scene pictures of 3D scene are discussed;thread synchronization mechanism is introduced;a 3D geographical scene was constructed to reflect the changes of soil erosion extent at three different time periods by overlaying true color remote sensing satellite images and DEM.This system has been used for showing the achievement of soil erosion control,and the effect sounds good.In addition to providing a strong immersion and big impact environment,the system also features dynamic change,enormous information,and strong expression.It has unique application capability for visualizing dynamic geographical scene.Last,these function modules are integrated in the 3D information system for synthetizing and management of virtual forest landscape(VisForest) which was designed and developed by research group coming from Spatial Information Research Centre of Fujian.

Using GIS Data to Build Informed Virtual Geographic Environments (IVGE)

In this paper, we propose a novel approach to automatically building Informed Virtual Geographic Environments (IVGE) using data provided by Geographic Information Systems (GIS). The obtained IVGE provides 2D and 3D geographic information for visualization and simulation purposes. Conventional VGE approaches are generally built upon a grid-based representation, raising the well-known problems of the lack of accuracy of the localized data and the difficulty to merge data with multiple semantics. On the contrary, our approach uses a topological model and provides an exact representation of GIS data, allowing an accurate geometrical exploitation. Moreover, our model can merge semantic information, even if spatially overlapping. In addition, the proposed IVGE contains spatial information which can be enhanced thanks to a geometric abstraction method. We illustrate this model with an application which automatically extracts the required data from standard GIS files and allows a user to navigate and retrieve information from the computed IVGE.

The Application Research on Voxel-Based Expression of the Virtual Geographical Environment

Due to the nature of the two-dimensional features of traditional “surface model” method for building the virtual geo-graphic environment, it is difficult to realistically simulate the real world of three-dimensional body. In this paper, fully understanding the basic concepts of voxels and features, based on the analysis of octree voxel model and rendering, we focus on the voxels in a virtual three-dimensional topography of the geographical environment for the simulation of natural phenomena, the expression of geographical process, spatial analysis and its research in the application. Also we discuss the virtual geographic environment which is based on “volumetric model”.

Crowd evacuation simulation for bioterrorism in micro-spatial environments based on virtual geographic environments

Urban management requires assessing bioterrorism response in micro-spatial environments, modeling potential attacks and carrying out efficient risk assessment. This paper presents the method of crowd evacuation simulation for bioterrorism in micro-spatial environments using the basic theory of Virtual Geographic Environments (VGE), combined with pathogen diffusion and crowd simulation modeling techniques. A framework of evacuation simulation was presented in this paper and the key technologies to implement the framework, including grid-based spatial data environment, agent-based individual model, and the method of associated individual behavior with spatial environment were also proposed to simulating crowd behaviors in bioterrorism. Taking the Olympic Park station of the Beijing Metro Line 8 as a typical study area, a crowd evacuation simulation prototype system was developed and a quasi-experiment using three different scenarios was conducted. The prototype system can be used to demonstrate some emergent individual behaviors in bioterrorism, such as competitive, queuing, and herding. Details can be obtained at each computation step (e.g., the number of people in subway station, the region of population, the geo-location of individual, the exposed population in polluted areas) with the prototype system. In the experiments, the number of people exposed is constantly increasing with the gradually increase of contaminant area as time pass. And different scenes were appeared for the different way of deal with bioterrorism. With the experiment, the number of people affected and the relevant parameters under various bioterrorism scenarios can be estimated, which can support rapid and efficient emergency decision-making for bioterrorism prevention.

Virtual Geographic Environment: A Workspace for Computer-Aided Geographic Experiments

A virtual geographic environment (VGE) is a type of workspace for computer-aided geographic experiments (CAGEs) and geographic analyses. By supporting geo-visualization, geo-simulation, geo-collaboration, and human participation, it provides open virtual environments that correspond to the real world to assist computer-aided geographic experiments involving both the physical and human dimensions. Based on a discussion of how VGEs can contribute to CAGEs and geographic analyses, this article proposes a clear, systematic framework for VGEs. Four subenvironments are discussed according to their different functions, pertinent issues, and corresponding solutions: (1) the data environment, (2) the modeling and simulation environment, (3) the interactive environment, and (4) the collaborative environment. Furthermore, a case on the simulation of air pollution and its analysis at different geographic scales is used to demonstrate VGEs’ ability to facilitate computer-aided geographic experiments.

Abstraction of informed virtual geographic environments

We propose a novel method for the automated generation of virtual geographic environments that allows using geographic information system data to build what we call informed virtual geographic environment (IVGE). The description of an IVGE integrates semantic information expressed using conceptual graphs, a standard knowledge representation technique. In addition, we propose an abstraction process that uses geometric, topologic, and semantic characteristics of geographic features to build a hierarchical graph-based structure describing this IVGE. Our IVGE model enables the support of large-scale and complex geographic environment modeling for multiagent geo-simulations in which the agents are situated and with which they interact.

A Virtual Geographic Environment for Simulation Analysis of Dam-Break Flood Routing

Dam-break flood affected by highly changing and complex environment, has some characteristics including the sudden of occurrence, the rapid of expansion and the urgency of respond. This paper focuses on how to develop a virtual geographic environment (VGE) system to study the dam-break flood routing and its impact. Unlike existing work, our methods pay attention to the multidimensional and dynamic analysis methods in virtual geographic environment, which make flood routing easily understood to public and officers. Moreover, some GIS spatial analysis and real-time interactive operation with the VGE will also be implemented to support the risk assessment of the dam-break. Finally, a prototype system is developed to construct a virtual geographic environment for impact analysis of dam-break flood routing and dynamic interaction. Experimental results prove that the scheme addressed in the paper is effective and feasible.

Growth Simulation of Young Chinese Fir Based on Virtual Plant

Energy fixation and organic matter production of forest ecosystem were dominated by plants,which are impacted by their growth environment.The forest ecosystem has the characteristic of long life-span,which makes its research laborious and costly using field experiment.The virtual geographical environment can provide a new way for its research due to its character of trying to exceed the limit of time and space.In order to estimate the biomass and evaluate relationships among tree and environments,an L-systems based functional-structural model was developed for simulating the development of tree architecture,taking into account tree physiology and environment.The L-systems was used to represent the morphological development of tree.The basic growth unit was described in line with the development of young Chinese fir(Cunninghamia lanceolata).LSTree system integrated the photosynthesis,photosynthates allocation and morphogenesis models.The spatial distribution of solar radiation in tree canopy was simulated for calculating photosynthetically active radiation(PAR) of each leaf obtained.PAR is a key parameter for photosynthesis model to estimate biomass.The dynamic growth of an individual 3-to-4-year-old Chinese fir in Fuzhou was simulated in growing season.Based on the 2010 Fuzhou weather and Chinese fir photosynthetic characteristic,net photosynthesis rate and product were calculated for each stage.The amount of photosynthates allocated to the growth of new segments and leaves or branches and leave amplification are based on source-sink theory.The growth of tree is driven by available photosynthetic products after respiration losses were accounted for.The morphogenesis change in the young Chinese fir in response to environment was simulated dynamically in three dimensional representations.The result of net photosynthesis was compared to the previous field observation research,and it showed the simulation result was reasonable.The methodology has promising benefits to depicting the interaction of plant and environment,which will be valuable for estimation of organic matter production too.

Algorithm of Mesh Generation of Feature Constraint-based Tetrahedralization

In the modeling process of Virtual Geographic Environment(VGE),as the geological objects generally have characteristics such as complex boundary,many spatial feature constraints including point,line,face and inside hole type,and meanwhile geosciences analysis and calculation require meshes with high quality,it is hard to construct three-dimensional meshes which regard for complex spatial feature constraints of geological objects exactly and have high quality for geosciences analysis and calculation.Aiming at this problem,a constrained Delaunay discrete algorithm of tetrahedral mesh is put forward in this paper.This algorithm first expresses constrained features of complex geological objects as a series of constraint points,constraint segments and constraint faces in Piecewise Linear Complexes(PLC),and then implements the initial Delaunay tetrahedral subdivision from the initial point set of the geological objects Piecewise Linear Complexes by using the Bowyer-Watson algorithm.Following the upper steps,the algorithm recovers the lost constraint lines and the lost constraint faces in sequence through adding some extra vertices during the mesh discrete process and it should guarantee the adding vertices do not encroach other constraint lines or constraint faces.The constraint face recovery is after the constraint line recovery and it is more difficult and complex than the constraint line recovery.In this step,some local meshes are demanded to reconstruct and must conform to the Delaunay empty circumsphere criterion.And then,the object model external tetrahedron elements should be deleted by adopting a marking method.After this step,it performs the mesh quality control process by restricting the maximum radius-distance ratio or the volume of tetrahedron element in the mesh.In this step,some extra vertices are also added in the tetrahedron elements which can not satisfy the user restricting quality.It is proved that the algorithm can produce meshes not only satisfying different constrained criteria but also with high quality for geosciences analysis and calculation.

Hierarchical Path Planning for Moving Agents in Informed Virtual Geographic Environments

Hierarchical Path Planning for Moving Agents in Informed Virtual Geographic Environments

Research and Implementation of Constructing Delaunay TIN Based on STL

Terrain Visualization is an important part in Research of Virtual Geographic Environments. A reasonable data structure and an efficient algorithm of constructing Terrain Model can ensure real-time rendering, query and interactive operation . Based on Standard Template Library in C++, The paper has designed a data structure of TIN, and improved Zhang Xiao-can's algorithm. At last, an application example is given.

Geographic analysis-oriented Virtual Geographic Environment: Framework, structure and functions

Previous research on the Virtual Geographic Environment (VGE) has focused mainly on representation rather than geographic analysis. However, geographic analysis plays a significant role in modern geography. To address this issue, this paper systematically examines theories and implementing VGE techniques that support geographical analysis and simulation. Based on its framework, VGE can be divided into four subtypes. These are the data environment, modeling environment, expression environment, and collaborative environment. The functions and key techniques of each are examined, and some case studies are discussed. This study provides direction for necessary new developments of advanced VGE platforms.

Collaborative virtual geographic environments: A case study of 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.

A framework to support qualitative reasoning about COAs in a dynamic spatial environment

We propose a framework to reason qualitatively about courses of action (COAs) which need to be executed in a realistic geographic space that may change. Particularly, the framework aims to support human mental ‘What-If’ analysis by simulating the execution of COAs in a virtual geographic environment, which can change during the simulation, and by allowing the user to explore various scenarios (different COAs) and to analyse their outcomes using causal reasoning techniques. In this article, we first present a framework which is based on a conceptual model of spatio-temporal situations, a multi-agent geosimulation platform and qualitative spatio-temporal causal reasoning techniques. Then, we illustrate the framework using a case study.

CUGrid and VGE Based Air Pollution Dispersion Simulation

Air pollution dispersion is a typical geographic process. A reasonable way to simulate air pollution dispersion is to modeling the dispersion and presents the results in a geographically referenced virtual environment. In this research, we apply the concept of virtual geographic environments (VGE), which is coined in the community of geographic information science, to facilitate air pollution dispersion by integrating MM5 and VGE. Because MM5 is computation intensive, the CUGrid is used in this research to decrease the computation time. Our research focuses on three key points, which are the platform design, MM5 integration and computation on CUGrid, and geographical visualization of air pollution dispersion in VGE. Based on the prototype system, a case of simulating air pollution dispersion in Pearl River Delta is employed to validate and test the rationality of the methodology. As shown in this case study, VGE can provide a good way to visualize air pollution dispersion and the CUGrid can decrease model computation time significantly.

Study Progress and Theorectical Framework of Virtual Geographic Environments

This paper explores the formation,development,and research status of virtual geographic environments(VGE),and discusses the concept of VGE in terms of virtual reality theory and techniques.A virtual geographic environment(VGE) is defined as a shared virtual space into which digital geographic objects and environments,as well as 3-D avatars,representing users or people in the physical environments,are transplanted.The characteristics of VGE are addressed from aspects of basic thoughts,system structure,and level of social organization of online participants.VGE systems include five kinds of spaces,namely Internet space,data space,3-D representation space,personal perceptual and cognitive space,and collaborative and social space.In view of online users,a VGE could be taken as an experimental laboratory or a system tool to deal with geo-scientific problems while the number of users is less,or as a virtual space or worlds in which numerous users are living and working.The relationship and differences among GIS,digital earth,and VGE are scrutinized,too.It is argued that VGE systems stem from the ultimate development of GIS and cartography,and are prototypes of Google Earth,Virtual Earth,EDUSHI,E-Urban,and Second Life.The key techniques,development of system platform,applications,and outlook of VGE are presented in terms of data,modeling,representation,and collaboration.The paper puts forward a fundamental theoretical framework of VGE from aspects of geographic philosophy and geographic sciences,and discusses issues related to human-oriented geographic information sciences,VGE based geographic scientific methodology,and computing man-land relationship.