3D city model is a digital model of urban areas that represent the surface of terrain, sites, buildings, vegetation, infrastructure, and landscape elements as well as related objects (eg urban furniture) included in urban areas. Their components are described and represented by corresponding two-dimensional and three-dimensional spatial data and geo-reference data. 3D city models support presentation, exploration, analysis, and management tasks in a large number of different application domains. In particular, the 3D city model allows "to integrate geoformation visually within a single framework and, therefore, create and manage complex urban information spaces."
Video 3D city models
Penyimpanan Model Kota 3D
To save the 3D city model, both file-based and database-based approaches are used. There is no single unique representation scheme due to the heterogeneity and diversity of 3d city model content.
Component Coding
The 3D city model components are encoded by common files and exchange formats for 2D raster-based GIS data (eg, GeoTIFF), 2D vector-based GIS data (eg AutoCAD DXF), 3D models (eg,.3DS,.OBJ), and 3D scenes (eg, Collada, Keyhole Markup Language) as supported by CAD, GIS, and computer graphics tools and systems. All components of the 3D city model must be converted to a common geo-coordinate system.
Database
The 3D city model database stores its components in a structured, multi-layered hierarchy, allowing stable and reliable data management and facilitating complex GIS modeling and analysis tasks. For example, the 3D City Database is a free 3D geo database to store, represent, and manage virtual 3D city models on top of standard spatial relational databases. A database is required if the 3D city model has to be sustainably managed. The 3D city model database forms a key element in 3D spatial data infrastructure that requires support for storing, managing, maintaining, and distributing 3D city model content. Its implementation requires support from multiple formats (eg, based on multiple FME formats). As a general application, geodata download portals can be set for 3D city model content (e.g., VirtualcityWarehouse).
CityGML
The Open Geospatial Consortium (OGC) defines an explicit XML-based exchange format for the 3D city model, CityGML, which supports not only geometric description of 3D city model components but also semantic and topology information specifications.
Maps 3D city models
3D City Model Constructions
Level Details
3D city models are usually built at various levels of detail (LOD) to provide insight into different resolutions and at different levels of abstraction. Other metrics such as spatio-semantic coherence level and texture resolution can be considered as part of LOD. For example, CityGML defines five LODs for building models:
- LOD 0: 2.5D footprint
- LOD 1: The building is represented by a block model (usually extruded footprints)
- LOD 2: Build a model with a standard roof structure
- LOD 3: Detail building model (architecture)
- LOD 4: LOD 3 building model with interior features.
There is also an approach to generalize the detailed 3D city model provided by using automated generalizations. For example, a hierarchical road network (eg, OpenStreetMap) can be used to group 3D city model components into "cells"; each cell is abstracted by combining and combining the components contained.
GIS data
GIS data provides basic information for building 3D city models such as digital terrain models, road networks, land use maps, and related geo-reference data. GIS data also includes cadastral data that can be transformed into simple 3D models, for example, in the case of extruded building footprints. The core components of the 3D city model form a digital field model (DTM) represented, for example, by TIN or lattice.
CAD data
Typical data sources for 3D city models also include CAD models of buildings, sites, and infrastructure elements. They provide a high level of detail, may not be required by 3D model city applications, but can be incorporated either by exporting their geometry or as packaged objects.
BIM data
Building an information model represents another category of geo-spatial data that can be integrated into a 3D city model that provides the highest level of detail for building components.
Integration at Visualization Level
The complex 3D city model is usually based on different geodata sources such as geodata from GIS, building and site models of CAD and BIM. It is one of their core properties to form a common reference frame for geo-spatial and heterogeneous geo-reference data, ie, data need not be merged or diffused based on a common data model or schema. Integration is possible by sharing a common geo-coordinate system at the visualization level.
Building Reconstruction
The simplest form of model construction consists of extrusion traces of building polygons, for example, taken from the cadastre, with an average pre-calculated height. In practice, the 3D model of urban area building is generated based on capturing and analyzing 3D point clouds (eg, samples by terrestrial or aerial laser scanning) or by photogrammetric approach. To achieve a high percentage of geometric 3D models and correct topological buildings, digital terrain surfaces and 2D trace polygons are required by automated building reconstruction tools such as BREC. One of the main challenges is finding parts of buildings with appropriate roof geometry. "Because fully automated image comprehension is very difficult to solve, semi-automatic components are usually required at least to support the introduction of highly complex buildings by human operators." The statistical approach is common to the reconstruction of the roof based on the cloud of airborne laser scanning points.
A fully automated process exists to produce a LOD1 and LOD2 building model for a large area. For example, the Bavarian Office for Spatial Surveys and Information is responsible for about 8 million building models in LOD1 and LOD2.
Visualization of 3D City Models
Visualization of the 3D city model represents the core functionality required for interactive applications and systems based on the 3D city model.
Real-Time Rendering 3D City Model
Providing high-quality visualization of large 3D city models in a scalable, fast, and cost-effective way is still a challenging task because of the complexity in terms of 3D geometry and 3D city model textures. Real-time rendering provides a large number of custom 3D rendering techniques for 3D city models. Examples of custom real time 3D rendering include:
- 3D views of real-time road networks on high-resolution terrain models.
- Real-time 3D water surface rendering with cartographic-oriented design.
- Real-time 3D viewing of the day and night sky phenomenon.
- Real-time 3D creation of a grid-based field model.
- Real-time 3D rendering uses different levels of abstraction, ranging from 2D map view and 3D view.
- Real-time 3D viewing from multiperspective view of 3D city model.
Real-time rendering algorithm and data structure registered by virtual field project.
3D-Based Service Modeling
Service-oriented architecture (SOA) to visualize 3D city models offers separation of concerns to management and rendering and their interactive provision by client applications. For SOA-based approaches, 3D imaging services are required, whose functionality primarily represents depiction in terms of 3D rendering and visualization. The SOA-based approach can be divided into two main categories, currently discussed in the Open Geospatial Consortium:
- 3D Web Services (W3DS): This service type handles geodata access and mapping to computer graphics primitives such as scene graphics with textured 3D geometry models as well as delivery to requested client applications. The client app is responsible for rendering 3D graphics of the submitted scene, that is, they are responsible for the interactive display using their own 3D graphics hardware.
- Web Display Service (WVS): This type of service summarizes the 3D rendering process for a 3D city model on the server side. The server generates a 3D scene view or an intermediate image-based image (for example, a virtual panorama or G-buffer cube map), which is streamed and uploaded to request the client application. The client application is responsible for rebuilding 3D scenes based on intermediate representations. The client application does not have to process 3D graphics data, but to provide management for loading, caching, and displaying 3D-based image representations and does not have to process the original 3D (and possibly large) 3D model.
Map-Based Visualization
A map-based technique, the "smart map" approach, aims to provide "large virtual 3D city models on different platforms, web browsers, smartphones or tablets, using interactive maps composed of artificial oblique image tiles." Map tiles are synthesized by an automatic 3D rendering process from the 3D city model; map tiles, generated for different levels of detail, are stored on the server. In this way, 3D rendering is fully done on the server side, simplifying access and use of the 3D city model. 3D rendering processes can apply advanced rendering techniques (for example, global illumination and shadow counting, decoding illustrations), but do not require that client devices have advanced 3D graphics hardware. Most importantly, the map-based approach makes it possible to distribute and use complex 3D city models by having to stream the underlying data to the client device - only previously created map tiles are sent. In this way, "(a) The complexity of 3D city model data separated from the complexity of data transfer (b) the application of client applications is significantly simplified because 3D rendering is summarized on the server side (c) 3D city model can be easily used for and used by a large number concurrent users, leading to high-level scalability of the overall approach. "
Apps
3D city models can be used for many purposes across a growing number of app domains. Example:
- Navigation system: 3D navigation maps have become ubiquitous in both automotive and pedestrian navigation systems, which include 3D city models, in particular, terrain models and 3D building models, to enhance visual imagery and to simplify location recognition.
- Urban Planning and Architecture: To organize, analyze, and disseminate urban planning concepts and projects, the 3D city model serves as a medium for communication and participation. The 3D city model provides a means for project communication, better acceptance of project development through visualization, and therefore avoids monetary losses through project delays; they also help prevent planning mistakes.
- Spatial Data Infrastructure (SDIs): 3D city models expand spatial data infrastructure and support the management, storage, and use of 3D models in SDI; they not only need tools and processes for early development and storage of 3D city models but also must provide efficient data management and data distribution to support workflows and applications.
- GIS: GIS supports 3D geodata and provides computational algorithms to create, modify, validate, and analyze components of the 3D city model.
- Emergency Management: For emergency, risk, and disaster management systems, the 3D city model provides a computing framework. Specifically, they serve to simulate fires, floods, and explosions. For example, the DETORBA project aims to simulate and analyze the effects of explosions in urban areas with high precision to support prediction of effects for structural integrity and urban infrastructure and safety health. preparation of rescue forces.
- Spatial Analysis: The 3D city model provides a computational framework for 3D spatial analysis and simulation. For example, they can be used to calculate the solar potential for a city's 3D roof surface, visibility analysis in urban space, noise simulation, building thermographic inspection
- Geodesign: In geodesign, 3D models of virtual environments (eg, landscape models or urban models) facilitate exploration and presentation as well as analysis and simulation.
- The game: The 3D city model can be used to get the basic data for virtual 3D scenes used in online games and videos.
- Cultural Heritage: The 3D city model tools and systems are applied to modeling, design, exploration, and analytical work within the sphere of cultural heritage. For example, archaeological data may be embedded in a 3D city model.
- City Information System: The 3D city model represents the framework for interactive 3D city information systems and 3D city maps. For example, cities are applying the 3D city model as a centralized information platform for location marketing.
- Property Management: The 3D city model technology can expand the systems and applications used in the management of real estate and property.
- Intelligent Transportation System: The 3D city model can be applied to intelligent transport systems.
- Augmented Reality: 3D city model can be used as a reference frame for augmented reality applications.
References
External links
- 3D City Model Systems and Tools Management and infrastructure components for the 3D city model.
- Map Based Visualization of 3D City Components Components for 3d city model applications.
- OGC 3D Portrayal IE Interoperability experiments depict images from the Open Geospatial Consortium.
- 3D City Model Berlin An example of a large 3D city model for urban areas.
- Classic City Model Roman Cologne A model example of a 3D city for cultural heritage applications.
Source of the article : Wikipedia
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