Application of 3D Digital Modeling Technology in the Construction of Digital Cities

The concepts of “digital twins”, “3D real scene”, “metacosm” and others were the technical paths for building digital cities with the development of emerging surveying and mapping science and technology, which was to build a digital and virtualized city that matched the real physical world, to achieve a one-to-one correspondence between all elements of the physical world and the digital virtual world. And one of its basic geographic information data was a highly similar, virtual simulation of the 3D real scene. After exploring the traditional manual 3DsMax modeling, UAV low-altitude digital oblique photogrammetry modeling, airborne laser scanning modeling and other single modeling technologies, this paper discussed the 3D digital modeling technology used by the UAV airborne laser scanning point cloud and low-altitude digital oblique photogrammetry for complementary integration, constructing the 3D scene of the digital city. This paper expounded the technical route and production process of 3D digital modeling, in order to provide technical references for related projects.

City Digital Twins: their maturity level and differentiation from 3D city models

The emerging field of City Digital Twins has advanced in recent years with the help of digital infrastructure and technologies connected to the Internet of Things(IoT).However,the evolution of this field has been so fast that a gap has opened in relation to systematic reviews of the relevant literature and the maturation of City Digital Twins on an urban scale.Our work bridges this gap by highlighting maturity in the field.We conducted a systematic literature review with bibliometric and content analysis of 41 selected papers published in Web of Science and Scopus data-bases,covering five areas:data types and sources,case studies,applied technologies and methods,maturity spectrum,and appli-cations.Based on maturity indicators,the majority of the reviewed studies(90%)were at initial to medium stages of maturity(up to element 3),most of them focused on 3D modelling,monitoring and visualisation.However,digital twins cannot be limited to 3D models,monitoring and visualisation,for they can be developed to include two-directional interactions between humans and com-puters.Such a high level of maturity,which was not found in the reviewed studies,requires advanced technologies and methods such as cloud computing,artificial intelligence,BIM and GIS.We also found that further studies are essential if the field is to handle the complex urban challenges of multidisciplinary digital twins.While City Digital Twins extend by definition beyond mere 3D city modelling,some studies involving 3D city models still refer to their subjects as City Digital Twins.Among the research gaps we identified,we’d like to highlight the need for near-real-time data analytics algorithms,which could furnish City Digital Twins with big data insights.Other opportunities include public participation capabilities to increase social collaboration,integrating BIM and GIS technologies and improving storage and computation infrastructure.

Geomatics for smart cities-concept,key techniques,and applications

The progressive transition from digital to smart cities has become a reality in recent years.Studies on the fundamental concept of smart cities,along with their supporting techniques,have attracted unprecedented attention.This study first discusses the concept of smart cities,where it is pointed out that the real city and the digital city can be integrated into a smart city by using ubiquitous sensor networks(USN)or the Internet of Things.More intelligent services for city management and public services can be provided in smart cities through massive and complex calculation,analysis,and data mining on cloud computing platforms.A smart city’s representative characteristics are summarized here to demonstrate that smart cities are superior for offering technical securities and intelligent services.Smart municipal supervision,smart transportation,smart environment monitoring,and smart tourism are used as examples to support the discussion.

Challenges and opportunities for the development of MEGACITIES

Urbanization is one of the most important social and economic phenomena in the world today.This paper reviews the formation of megacities and summarizes the main problems,challenges and opportunities faced by the sustainable development of such large megacities.Issues discussed include the problems of land subsidence in megacities,environmental issues,traffic problems and energy supply aspects.The sustainable development of megacities in other parts of the world provided the references and experiences for the countermeasures of megacity planning and development in China.The vision of Digital Earth and Digital Cities can play a major role in the efficient management and sustainable growth of such megacities all around the world.

Simulated impacts of 3D urban morphology on urban transportation in megacities: case study in Beijing

Urban morphology and morphology change and their impacts on urban transportation have been studied extensively in planar urban space.The essential feature of urban space,however,is its three-dimensionality(3D),and few studies have been conducted from a 3D perspective,overly limiting the accuracy of studies on the relationships between urban morphology and transportation.The aim of this paper is to simulate the impacts of 3D urban morphologies on urban transportation under the Digital Earth framework.On the basis of the principle that population distribution and movement are largely confined by 3D urban morphologies,which affect transportation,high spatial resolution remote sensing imagery and a thematic vector data-set were used to extract urban morphology and transportation-related variables.With a combination of three research methods-factor analysis,spatial regression analysis and Euclidean allocation-we provide an effective method to construct a simulation model.The paper indicates three general results.First,building capacity in the urban space has the most significant impact on traffic condition.Second,obvious urban space otherness,reflecting both use density characteristics and functional character-istics of urban space,mostly results in heavier traffic flow pressure.Third,no single morphology density indicator or single urban structure indicator can reflect its contribution to the pressure of traffic flow directly,but a combination of these different indicators has the ability to do so.

Enhanced urban functional land use map with free and open-source data

The study aims at developing an applicable methodology to produce the functional land-use map using only free and open-source data.Top-view Sentinel image and ground-view Open Street Map(OSM)data are chosen due to their extensive availability.The three-stage framework,including object-based image analysis,OSM data cleaning,and ontology-based decision fusion,is proposed and implemented with open-source tools.We applied the developed approach to districts 1,4,and 7 of HoChiMinh city,representing the complexities of the dynamic change in big cities.The result showed a good functional land use map with 78.70%overall accuracy.The outcome presents the mismatch between the data-driven approach and human knowledge,which can be improved by ontology-based fusion with OSM data.The ontology-based framework comprises the common urban land-use classes and OSM attributes,which can be applied and extended in other urban areas.Additional text attributes may be applicable only locally and can be modified in our open-source framework.Object-based image analysis takes advantage of Google Earth Engine computing power,whereas ontology-based processing works well on a local computer.In future studies,adopted natural language processing to pre-process OSM data and ontology-based fusion will be implemented on the cloud-computing platform to enhance computational efficiency.

Toward optimizing the design of virtual environments for route learning:empirically assessing the effects of changing levels of realism on memory

Broadly,this paper is about designing memorable 3D geovisualizations for spatial knowledge acquisition during(virtual)navigation.Navigation is a fundamentally important task,and even though most people navigate every day,many find it difficult in unfamiliar environments.When people get lost in an unfamiliar environment,or are unable to remember a route that they took,they might feel anxiety,disappointment and frustration;and in real world,such incidents can be costly,and at times,life-threatening.Therefore,in this paper,we study the design decisions in terms of visual realism in a city model,propose a visualization design optimized for route learning,implement and empirically evaluate this design.The evaluation features a navigational route learning task,where we measure shortand long-term recall accuracy of 42 participants with varying spatial abilities and memory capacity.Our findings provide unique empirical evidence on how design choices affect memory in route learning with geovirtual environments,contributing toward empirically verified design guidelines for digital cities.