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A Multiple Representation Data Structure for Dynamic Visualisation of Generalised 3D City Models
KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
Department of Physical Geography and Ecosystem Analysis, Lund University. (GIS Centre)
2011 (English)In: ISPRS journal of photogrammetry and remote sensing (Print), ISSN 0924-2716, E-ISSN 1872-8235, Vol. 66, no 2, 198-208 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, a novel multiple representation data structure for dynamic visualisation of 3D city models, called CityTree, is proposed. To create a CityTree, the ground plans of the buildings are generated and simplified. Then, the buildings are divided into clusters by the road network and one CityTree is created for each cluster. The leaf nodes of the CityTree represent the original 3D objects of each building, and the intermediate nodes represent groups of close buildings. By utilizing CityTree, it is possible to have dynamic zoomfunctionality in real time. The CityTree methodology is implemented in aframework where the original city model is stored in CityGML and the CityTree is stored as X3D scenes. A case study confirms the applicability of the CityTree for dynamic visualisation of 3D city models.

Place, publisher, year, edition, pages
2011. Vol. 66, no 2, 198-208 p.
National Category
Other Computer and Information Science
Identifiers
URN: urn:nbn:se:kth:diva-24707DOI: 10.1016/j.isprsjprs.2010.08.001ISI: 000288628000006Scopus ID: 2-s2.0-79951727298OAI: oai:DiVA.org:kth-24707DiVA: diva2:352942
Note
QC 20110530Available from: 2010-09-23 Created: 2010-09-23 Last updated: 2017-12-12Bibliographically 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
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

3D city models have been widely used in different applications such as urban planning, traffic control, disaster management etc. Effective visualisation of 3D city models in various scales is one of the pivotal techniques to implement these applications. In this thesis, a framework is proposed to visualise the 3D city models both online and offline using City Geography Makeup Language (CityGML) and Extensible 3D (X3D) to represent and present the models. Then, generalisation methods are studied and tailored to create 3D city scenes in multi-scale dynamically. Finally, the quality of generalised 3D city models is evaluated by measuring the visual similarity from the original models.

 

In the proposed visualisation framework, 3D city models are stored in CityGML format which supports both geometric and semantic information. These CityGML files are parsed to create 3D scenes and be visualised with existing 3D standard. Because the input and output in the framework are all standardised, it is possible to integrate city models from different sources and visualise them through the different viewers.

 

Considering the complexity of the city objects, generalisation methods are studied to simplify the city models and increase the visualisation efficiency. In this thesis, the aggregation and typification methods are improved to simplify the 3D city models.

 

Multiple representation data structures are required to store the generalisation information for dynamic visualisation. One of these is the CityTree, a novel structure to represent building group, which is tested for building aggregation. Meanwhile, Minimum Spanning Tree (MST) is employed to detect the linear building group structures in the city models and they are typified with different strategies. According to the experiments results, by using the CityTree, the generalised 3D city model creation time is reduced by more than 50%.

 

Different generalisation strategies lead to different outcomes. It is important to evaluate the quality of the generalised models. In this thesis a new evaluation method is proposed: visual features of the 3D city models are represented by Attributed Relation Graph (ARG) and their similarity distances are calculated with Nested Earth Mover’s Distance (NEMD) algorithm. The calculation results and user survey show that the ARG and NEMD methods can reflect the visual similarity between generalised city models and the original ones.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. x, 60 p.
Series
Trita-SOM , ISSN 1653-6126 ; 2010:8
Keyword
3D city models, Visualisation, CityGML, X3D, Generalisation, Aggregation, Typification, Quality evaluation
National Category
Computer and Information Science
Research subject
SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-24345 (URN)978-91-7415-715-4 (ISBN)
Presentation
2010-09-10, Seminarierum 4055, Drottning Kristinas väg 30, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
ViSuCity Project
Funder
Swedish e‐Science Research Center
Note
QC 20100923Available from: 2010-09-23 Created: 2010-09-02 Last updated: 2010-09-23Bibliographically approved
2. 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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