Liangchen Zhou

Data environment construction for virtual geographic environment

Virtual geographic environment (VGE) aims to express the real-world naturally, and support the complex geographic analysis. The data environment, fundamental of VGE, is expected to support the data management, analysis, sharing and application requirements of the massive complex geographic spatio-temporal data. In this paper, we summarized the key problems in the construction of the data environment of VGE. The unified spatio-temporal data model and a new data structure were developed according to the geographic rules. The organization and compress storage mechanism of massive spatio-temporal data were also developed. With these foundations, case studies, which integrate the global, regional and city scale data to operate complex data modeling and analysis, are performed. The results showed that the construction of the integrated data environment of VGE can largely improve the efficiency of GIS analysis, which also provides a potential new tool to support the complex geographic analysis.

Geographic scenario: a possible foundation for further development of virtual geographic environments

ABSTRACT It has been two decades since virtual geographic environments (VGEs) were initially proposed. While relevant theories and technologies are evolving, data organization models have always been the foundation of VGE development, and they require further exploration. Based on the comprehensive consideration of the characteristics of VGEs, geographic scene is proposed to organize geographic information and data. We empirically find that geographic scene provides a suitable organization schema to support geo-visualization, geo-simulation, and geo-collaboration. To systematically investigate the concept and method of geographic scene, Geographic Scenario is proposed as the theory on developing geographic scene, and corresponding key issues of the Geographic Scenario are illustrated in this article. Prospects of the proposed method are discussed with the hope of informing future studies of VGEs.

Research on novel 3D buffer analysis method based on vector

Spatial buffer analysis is one of the important and basic spatial operation functions of geographic information system. Studying 2D spatial buffer generation and analysis was more than the 3D spatial presently, thereby a novel 3D buffer generation algorithm based on vector was presented in this paper. 3D spatial solid is represented by B-Rep model and its buffer is categorized into solid boundary buffer and solid interior, then construct the whole buffer by union operation on them. The boundary features of 3D spatial solid are classified into point feature, line features and face features. Usually, the statistical analysis is necessary after solid buffer generation. Thus, we proposed a new method which can quick judge whether the buffer affecting the surrounding objects based on collision detection theory. Finally, taking the surface and underground 3D space around University City region of Xianlin as the research area, a 3D buffer with complex geological environment and man-made buildings is created based on the new presented algorithm, and spatial statistical analysis is achieved based on the generated 3D buffer. The results show that the improved algorithm is efficient and practicable, especially the proposed 3D buffer generation algorithm based on vector is applicable for convex body and concave body comparing with current approaches.

Extracting Indoor Space Information in Complex Building Environments

Indoor space information extraction is an important aspect of reconstruction for building information modeling and a necessary process for geographic information system from outdoor to indoor. Entity model extracting methods provide advantages in terms of accuracy for building indoor spaces, as compared with network and grid model methods, and the extraction results can be converted into a network or grid model. However, existing entity model extracting methods based on a search loop do not consider the complex indoor environment of a building, such as isolated columns and walls or cross-floor spaces. In this study, such complex indoor environments are analyzed in detail, and a new approach for extracting buildings’ indoor space information is proposed. This approach is based on indoor space boundary calculation, the Boolean difference for single-floor space extraction, relationship reconstruction, and cross-floor space extraction. The experimental results showed that the proposed method can accurately extract indoor space information from the complex indoor environment of a building with geometric, semantic, and relationship information. This study is theoretically important for better understanding the complexity of indoor space extraction and practically important for improving the modeling accuracy of buildings.

3D GIS spatial operation based on extended Euler operators

The implementation of 3 dimensions spatial operations, based on certain data structure, has a lack of universality and is not able to treat with non-manifold cases, at present. ISO/DIS 19107 standard just presents the definition of Boolean operators and set operators for topological relationship query, and OGC GeoXACML gives formal definitions for several set functions without implementation detail. Aiming at these problems, based mathematical foundation on cell complex theory, supported by non-manifold data structure and using relevant research in the field of non-manifold geometry modeling for reference, firstly, this paper according to non-manifold Euler-Poincaré formula constructs 6 extended Euler operators and inverse operators to carry out creating, updating and deleting 3D spatial elements, as well as several pairs of supplementary Euler operators to convenient for implementing advanced functions. Secondly, we change topological element operation sequence of Boolean operation and set operation as well as set functions defined in GeoXACML into combination of extended Euler operators, which separates the upper functions and lower data structure. Lastly, we develop underground 3D GIS prototype system, in which practicability and credibility of extended Euler operators faced to 3D GIS presented by this paper are validated.

Visualization analysis based on cell complex for 3D GIS

As the theory and application requirement of 3d GIS are developing dramatically, 3D geological simulation is not only limited in the capability of visualizing spatial objects, and it has a deeper demand on three dimensions spatial analysis for geographic objects or phenomenon. Therefore, a lot of visualized analysis functions for practical projects are proposed by researchers. However, these researches usually come up with corresponding algorithms based on certain data model or data structure which is without a powerful portability. And the algorithms are often limited to specific requirement which has little expansibility. To solve this problem, a new 3D GIS data model for 3D geological simulation is advanced based on cell complex theory and correlative research results in the field of non-manifold geometric modeling. And a series of 3D set operators are defined to carry out virtual drilling, virtual cutting, virtual digging and virtual tunnel excavation analysis and so on. Compared with existing implementations, the new presented 3D GIS data model unifies the expression of wire frame, facial and volumetric model, which ensures the portability of algorithm. Set operators based on non-manifold geometric modeling possessing mathematical completeness have the ability to implement arbitrary geometric object operation, which can insure the expansibility of the algorithm.