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Online Visualisation of a 3D City Model Using CityGML and X3DOM
KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
2011 (English)In: Cartographica, ISSN 0317-7173, E-ISSN 1911-9925, Vol. 46, no 2, 109-114 p.Article in journal (Refereed) Published
Abstract [en]

This article proposes a novel framework for online visualization of 3D city models. CityGML is used to represent the city models, based on which 3D scenes in X3D are generated, then dynamically updated to the user side with AJAX and visualized in WebGL-supported browsers with X3DOM. The experimental results show that the proposed framework can easily be implemented using widely supported major browsers and can efficiently support online visualization of 3D city models in small areas. For the visualization of large volumes of data, generalization methods and multiple-representation data structure should be studied in future research.

Place, publisher, year, edition, pages
2011. Vol. 46, no 2, 109-114 p.
Keyword [en]
3D modelling, visual language for GIS, Web mapping
National Category
Other Computer and Information Science
Research subject
SRA - ICT
Identifiers
URN: urn:nbn:se:kth:diva-48156DOI: 10.3138/carto.46.2.109Scopus ID: 2-s2.0-79955632348OAI: oai:DiVA.org:kth-48156DiVA: diva2:456879
Note

QC 20111116

Available from: 2011-11-16 Created: 2011-11-16 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Visualisation and Generalisation of 3D City Models
Open this publication in new window or tab >>Visualisation and Generalisation of 3D City Models
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

3D city models have been widely used in various applications such as urban planning, traffic control, disaster management etc. Efficient visualisation of 3D city models in different levels of detail (LODs) is one of the pivotal technologies to support these applications. In this thesis, a framework is proposed to visualise the 3D city models online. Then, generalisation methods are studied and tailored to create 3D city scenes in different scales dynamically. Multiple representation structures are designed to preserve the generalisation results on different level. Finally, the quality of the generalised 3D city models is evaluated by measuring the visual similarity with the original models.

 

In the proposed online visualisation framework, City Geography Makeup Language (CityGML) is used to represent city models, then 3D scenes in Extensible 3D (X3D) are generated from the CityGML data and dynamically updated to the user side for visualisation in the Web-based Graphics Library (WebGL) supported browsers with X3D Document Object Model (X3DOM) technique. The proposed framework can be implemented at the mainstream browsers without specific plugins, but it can only support online 3D city model visualisation in small area. For visualisation of large data volumes, generalisation methods and multiple representation structures are required.

 

To reduce the 3D data volume, various generalisation methods are investigated to increase the visualisation efficiency. On the city block level, the aggregation and typification methods are improved to simplify the 3D city models. On the street level, buildings are selected according to their visual importance and the results are stored in the indexes for dynamic visualisation. On the building level, a new LOD, shell model, is introduced. It is the exterior shell of LOD3 model, in which the objects such as windows, doors and smaller facilities are projected onto walls.  On the facade level, especially for textured 3D buildings, image processing and analysis methods are employed to compress the texture.

 

After the generalisation processes on different levels, multiple representation data structures are required to store the generalised models for dynamic visualisation. On the city block level the CityTree, a novel structure to represent group of buildings, is tested for building aggregation. According to the results, the generalised 3D city model creation time is reduced by more than 50% by using the CityTree. Meanwhile, a Minimum Spanning Tree (MST) is employed to detect the linear building group structures in the city models and they are typified with different strategies. On the building level and the street level, the visible building index is created along the road to support building selection. On facade level the TextureTree, a structure to represent building facade texture, is created based on the texture segmentation.

 

Different generalisation strategies lead to different outcomes. It is critical to evaluate the quality of the generalised models. Visually salient features of the textured building models such as size, colour, height, etc. are employed to calculate the visual difference between the original and the generalised models. Visual similarity is the criterion in the street view level building selection. In this thesis, the visual similarity is evaluated locally and globally. On the local level, the projection area and the colour difference between the original and the generalised models are considered. On the global level, the visual features of the 3D city models are represented by Attributed Relation Graphs (ARG) and their similarity distances are calculated with the Nested Earth Mover’s Distance (NEMD) algorithm.

 

The overall contribution of this thesis is that 3D city models are generalised in different scales (block, street, building and facade) and the results are stored in multiple representation structures for efficient dynamic visualisation, especially for online visualisation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xii, 104 p.
Series
Trita-SOM , ISSN 1653-6126 ; 2011>19
Keyword
3D city models, visualisation, generalisation, multiple representation structure, similarity evaluation, aggregation, typification, shell model, street index, texture compression, texture segmentation
National Category
Other Environmental Engineering
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-48174 (URN)978-91-7501-189-9 (ISBN)
Public defence
2011-12-02, D2, Lindstedtsvägen 5, Entreplan, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
ViSuCity
Note
QC 20111116Available from: 2011-11-16 Created: 2011-11-16 Last updated: 2011-11-16Bibliographically approved

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