Zhang Yeting

Integration method of TINs and Grids for multi-resolution surface modeling

Highly detailed surface models and their real-time applications are increasingly popular in architecture, construction and other design and engineering fields. However, new and related problems have emerged concerning the efficient management of the resulting large datasets and the seamless integration of heterogeneous data. Moreover, the increasingly common requirements of local high-fidelity modeling combined with large-scale landscapes lead to difficulty in the seamless multi-resolution representation of hybrid triangulated irregular networks (TINs) and Grids. This paper presents a hybrid data structure with high-efficiency and a related organizational method for the seamless integration of multi-resolution models. This approach is characterized by (1) a self-adaptive algorithm for feature-preserving surface partitioning, (2) an efficient hybrid index structure for combined Grid and TIN surfaces, and (3) a view-dependent scheduling strategy with access to Grids of necessary resolution, giving priority to the dynamic loading of TINs. Experiments using typical real design datasets of highway constructions are able to achieve accuracy-preserved and real-time availability of results that prove the validity and efficiency of this approach.

An oracle-based data management method for large database in CyberCity GIS

An Oracle8i-based approach is proposed to manage the integrated databases of large CyberCity. This approach consists of three schemes: ⨢ a special R+-tree index is designed to accelerate spatial retrieving, in which the bounding boxes of local regions have no intersection and all leaf nodes of the R+-tree (geometry records) have no repetition; ∪ different data compression algorithms are adopted to compress the digital elevation models, 3D vector models and images, such as LZ77 lossless compression algorithm for compression of vector data and JPEG compression algorithms for texture images; ⥲ in order to communicate with Oracle8i database, a CyberCity GIS spatial database engine (SDE) is designed. On the basis of this SDE prototype a case study is done.

Spatial decision support applications based on three-dimensional city models

The basic mathematic models, such as the statistic model, the time-serial model, the spatial dynamic model etc., and some typical analysis methods based on 3DCM are proposed and discussed. A few typical spatial decision making methods integrating the spatial analysis and the basic mathematical models are also introduced, e.g. visual impact assessment, dispersion of noise immissions, base station plan for wireless communication. In addition, a new idea of expectation of further applications and add-in-value service of 3DCM is promoted. As an example, the sunshine analysis is studied and some helpful conclusions are drawn.

Texture data storage method based on hierarchical spatial index

Aiming at the massive data organization and management of textures with various sizes for real-time rendering of large-scale 3D city models, this paper proposes a new method: a texture spatial index tree is built up based on the hierarchical spatial index of 3D geometries, and then the texture data is written into mapping files structure through depth-first and hierarchical iteration for the clustering of data blocks, which facilitates the flexible size-changed disk I/O operations. Experimental results prove such kind of storage is more compact and more effective than single file storage method, and enables the fast access of texture data.