An integrated virtual geographic environmental simulation framework:a case study of flood disaster simulation

Dynamic flood disaster simulation is an emerging and promising technology significantly useful in urban planning,risk assessment,and integrated decision support systems.It is still an important issue to integrate the large assets such as dynamic observational data,numerical flood simulation models,geographic information technologies,and computing resources into a unified framework.For the intended end user,it is also a holistic solution to create computer interpretable representations and gain insightful understanding of the dynamic disaster processes,the complex impacts,and interactions of disaster factors.In particular,it is still difficult to access and join harmonized data,processing algorithms,and models that are provided by different environmental information infrastructures.In this paper,we demonstrate a virtual geographic environments-based integrated environmental simulation framework for flood disaster management based on the notion of interlinked resources,which is capable of automated accumulating and manipulating of sensor data,creating dynamic geo-analysis and three-dimensional visualizations of ongoing geo-process,and updating the contents of simulation models representing the real environment.The prototype system is evaluated by applying it as a proof of concept to integrate in situ weather observations,numerical weather and flood disaster simulation models,visualization,and analysis of the real time flood event.Case applications indicate that the developed framework can be adopted for use by decision-makers for short-term planning and control since the resulting simulation and visualization are completely based on the latest status of environment.

Geographic scenario:a possible foundation for further development of virtual geographic environments

It has been two decades since virtual geographic environments(VGEs)were initially proposed.While relevant theories and technologies are evolving,data organization models have always been the foundation of VGE development,and they require further exploration.Based on the comprehensive consideration of the characteristics of VGEs,geographic scene is proposed to organize geographic information and data.We empirically find that geographic scene provides a suitable organization schema to support geo-visualization,geo-simulation,and geo-collaboration.To systematically investigate the concept and method of geographic scene,Geographic Scenario is proposed as the theory on developing geographic scene,and corresponding key issues of the Geographic Scenario are illustrated in this article.Prospects of the proposed method are discussed with the hope of informing future studies of VGEs.

Literary placemaking and narrative immersion in extended reality virtual geographic environments

Virtual geographical environments(VGEs)are being used to represent our sense of place through the application of extended-reality or cross-reality(XR)technologies with a focus on technological advancement and immersion.In light of this,we propose that an expanded and interdisciplinary understanding of the concept of immersion is required to facilitate an understanding of spatial data to a broader audience.The potential of focusing on narrative immersion and literary placemaking in VGEs is discussed to evoke a stronger sense of place and a feeling of presence and belonging in users.This paper seeks to highlight the unique affordances and potentialities of XR narrative style GIS digital representations through an interdisciplinary theoretically lead analysis of outputs created by the Building City dashboards project towards the goal of expanding audiences of non-specialist stakeholders in urban planning processes.

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.

Spatial simulation using abstraction of virtual geographic environments

In this paper,we address two challenging issues underlying spatial simulation using software agents immersed in virtual geographic environments(VGE).First,the way to describe virtual VGE models using accurate spatial decomposition approaches structured using graph theory techniques.Second,the use of graph abstraction techniques to support realistic and advanced navigation and path planning capabilities for software agents considering the VGE’s characteristics.In order to illustrate our contributions to the growing field of spatial simulations,we present and discuss a case study involving an urban VGE model populated with agents who autonomously and differently interact with multiple abstractions of the same physical environment.

Deep reinforcement learning and 3D physical environments applied to crowd evacuation in congested scenarios

To avoid crowd evacuation simulations depending on 2D environments and real data,we propose a framework for crowd evacuation modeling and simulation by applying deep reinforcement learning(DRL)and 3D physical environments(3DPEs).In 3DPEs,we construct simulation scenarios from the aspects of geometry,semantics and physics,which include the environment,the agents and their interactions,and provide training samples for DRL.In DRL,we design a double branch feature extraction combined actor and critic network as the DRL policy and value function and use a clipped surrogate objective with polynomial decay to update the policy.With a unified configuration,we conduct evacuation simulations.In scenarios with one exit,we reproduce and verify the bottleneck effect of congested crowds and explore the impact of exit width and agent characteristics(number,mass and height)on evacuation.In scenarios with two exits and a uniform(nonuniform)distribution of agents,we explore the impact of exit characteristics(width and relative position)and agent characteristics(height,initial location and distribution)on agent exit selection and evacuation.Overall,interactive 3DPEs and unified DRL enable agents to adapt to different evacuation scenarios to simulate crowd evacuation and explore the laws of crowd evacuation.

Improved Cubemap model for 3D navigation in geo-virtual reality

Due to advances in rendering techniques and hardware capability,stereoscopic 3D(s3D)visualization is becoming increasingly common in daily life.However,this does not change the fact that stereo effects and visual comfort depend greatly on how the related parameters are controlled during the production of the s3D images.In geovirtual reality systems,which are important browsers for Digital Earth,the maintenance of these parameters is deeply related to the navigation process.Therefore,the navigation method in such systems requires special care.This paper presents a new flying method based on a Cubemap structure.The method defines a Vehicle model and modifies the original Cubemap structure by adding a front view camera during the navigation;it allows the users to fly through a virtual geographic environment with automatic speed control,smooth collision resolution,and dynamic adjustment of the s3D-related parameters.A user test was conducted to compare this new method with the original method based on the Cubemap structure.The results show that the new method performs better than the former one for it provides a convenient interaction experience with improved stereoscopic effect,and diminishes visual discomfort.

Adaptive step-size forward advection method for aerosol process simulation

Outdoor aerosol processes are often associated with disasters and diseases,which threaten human life and health.Outdoor aerosols are afluid system affected by meteorological conditions and three-dimensional complex terrain.Their variable wind speed and direction and complex terrain boundary conditions make simulating advection processes difficult.Based on incompressibleflow conditions,we designed an adaptive time step algorithm for forward advection for the rapid simulation of aerosol processes.The method is based on thefirst-order forward semi-Lagrangian advection method with unconditional mass conservation.Thefirst-order truncated error coefficient function theory generates an adaptive time step to control the accuracy of forward advection.Smoke aerosol simulation experiments in two small outdoor scenes were designed,and the effects of the traditional backward advection and forwardfixed step methods were compared with the algorithm in this study.The proposed simulation method showed improved accuracy compared with the other two methods in experimental scenarios;moreover,compared with those of the traditional backward method,the computation time was significantly reduced and the conservation of mass was significantly improved.Thus,the proposed method is a fast simulation method for outdoor aerosol numerical prediction.KEY POLICY HIGHLIGHTS.The first-order forward semi-Lagrangian method,which requires no iteration and less computation and offers unconditional conservation,was used..The law of truncation error coefficient of thefirst-order forward method was studied and an adaptive step algorithm was designed..Full-size real aerosol experiments in small-scale complex outdoor scenes were conducted for verification and comparison of simulation effects.

An efficient flood dynamic visualization approach based on 3D printing and augmented reality

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,augmented flood visualizations that support decision makers’perspectives are needed,which can be enhanced by emerging augmented reality(AR)and 3D printing technologies.This paper proposes an innovative flood AR visualization method based on a 3D-printed terrain model and investigates essential techniques,such as the suitable size calculation of the terrain models,the adaptive processing of flood data,and hybridizing virtual flood and terrain models.A prototype experimental system(PES)based on the proposed method and a comparison experimental system(CES)based on a virtual terrain are developed to conduct comparative experiments,which combine the system performance and questionnaire method to evaluate the efficiency and usability of the proposed method.The statistical results indicate that the method is useful for assisting participants in understanding the flood hazard and providing a more intuitive and realistic visual experience compared with that of the traditional AR flood visualization method.The frame rate is stable at 60 frames per second(FPS),which means that the proposed method is more efficient than the traditional AR flood visualization method.

Camera localization for augmented reality and indoor positioning:a vision-based 3D feature database approach

The recent fast development in computer vision and mobile sensor technology such as mobile LiDAR and RGB-D cameras is pushing the boundary of the technology to suit the need of real-life applications in the fields of Augmented Reality(AR),robotics,indoor GIS and self-driving.Camera localization is often a key and enabling technology among these applications.In this paper,we developed a novel camera localization workflow based on a highly accurate 3D prior map optimized by our RGBD SLAM method in conjunction with a deep learning routine trained using consecutive video frames labeled with high precision camera pose.Furthermore,an AR registration method tightly coupled with a game engine is proposed,which incorporates the proposed localization algorithm and aligns the real Kinetic camera with a virtual camera of the game engine to facilitate AR application development in an integrated manner.The experimental results show that the localization accuracy can achieve an average error of 35 cm based on a fine-tuned prior 3D feature database at 3 cm accuracy compared against the ground-truth 3D LiDAR map.The influence of the localization accuracy on the visual effect of AR overlay is also demonstrated and the alignment of the real and virtual camera streamlines the implementation of AR fire emergency response demo in a Virtual Geographic Environment.

Versioned geoscientific workflow for the collaborative geosimulation of human-nature interactions-a case study of global change and human activities

Global change refers to changes in the relationship between humans and nature.It is desirable to actively integrate human social activities into the unified framework of global change so that their mutual relations and functional mechanisms can be understood.This complicated issue necessitates an appropriate method allowing domain experts to collaboratively contribute their knowledge to geoscientific research.Also,an efficient approach to optimize experimentation is of great importance.The reproducibility of research methods and results needs to be improved to boost the sharing of geographic knowledge and resources.This paper proposes a versioned geoscientific workflow and characterizes its full lifecycle using Virtual Geographic Environments,intending to facilitate and improve research related to the interactions between global change and human activities.The geoscientific workflow management is realized using the concept of version management,making geographic simulation methods and computational results easily reproducible and extendable.The sharing and reuse of geographic knowledge in various forms are archived through version management of geoscientific workflows.A versatile prototype system is implemented which enables the visual modeling of geoscientific workflows,the interactive optimization and collaborative evaluation of geoscientific workflows at runtime,the multi-dimensional dynamic visualization of geo-workflow outputs,and role-based access control for data security.