Study On Aground-Underground Seamlessly Integrated Multi-LOD Modeling And Application

As the construction of Digital City, Digital Mine, Digital Regional and Digital Earth being comprehensively promoted; human activities on aground, surface and underground have expanded continuously. Aground-underground seamlessly integrated modeling basing on information fusion and data integration becomes an important direction of 3DGIS. However, traditional cognitive activities with purpose of a single space or a small area were difficult to meet the needs of economic and social development, many key technologies such as aground-underground 3D complex object geometric seamlessly integrated modeling and multi-resolution need to be investigated, the following issues need to be resolved:(1) although some studies involving the ground scene, terrain, underground works and ore joint visualization, but those mostly emphasized on independent modeling, hardly considering the seamless integration issues; (2) The traditional multi-scale modeling in the field were more concerned about a single space (such as multi-scale modeling of terrain or buildings), and less in involving two layers’multi-scale modeling, therefore, taking into account of aground, surface and underground three-space integrated multi-scale modeling should be solved.This paper basing on reviewing and summarizing the results of previous studies established the multi-scale models of aground, terrain and underground space goals as well as the interactive relationship between the models, with extensions and amendments of aground-underground integrated 3D spatial data model, several key issues about aground-underground seamlessly integrated multi-lod modeling had been studied.Spatial data integration is composed of the integration of raw data and modeling results data. Original data integration emphasizes on merging different types and different sources data together in order to form effective rules to support uniform expression of raw data. The result data integration refers to unified presentation of the data set after a series of operations to original data such as modeling, analysis, and application, so as to address a complete description of geological entities and the seamlessly integrated expression of geosciences space. In essence, spatial data integration was accomplished by extracting the common of different space model and finding its associated point for the seamless integration. The triangle data collection with appropriate data structure achieved the expression of different physical models, by topological structure addressed the relationship between different models together with the conversion from each other. After analyzing the principle of spatial data integration based on the TTS, a framework for data integration and data organization structure were given.After analyzing the multi-level demand of geosciences space modeling, a logical structure with semantic heterogeneity as driving force, multi-scale geosciences data as basis, multi-scale geosciences model as exhibition, relationship between each other as support has been built up. Furthermore, combined with domain knowledge and practical applications, considering the semantic differences, a multi-lod model with linkage mechanism of aground, surface and underground, containing six semantic levels, had been designed, which contributed to the seamlessly integrated modeling of aground, surface and underground.In aground-underground seamlessly integrated modeling there are several geometric borders, mainly include:boundary between entities aground (buildings, roads, bridges, etc.) and the surface; border of surface and the geological body; side border of aground, surface and underground entities. At geometric boundaries above, the following problems may arise: the stratigraphic model covers the surface model; and the side border gap of integrated model may happen. After analyzing the causes of the two kinds of gaps, corresponding solution method had been investigated.The integrated spatial data model is the key of aground-underground seamlessly integrated modeling, with analyzing the principle of aground and underground objects geometric seamless integration, based on the CSG+CD-TIN+GTP integrated model, the TTS had been integrated so as to form a Aground-Underground Seamlessly Integrated Model(AU-SIM), and the key model structure is CSG+CD-TIN+GTP—TTS. Coupling the principles of seamlessly integrated modeling with the mechanism of multi-scale modeling, a typical architecture considering semantics of aground-underground seamlessly integrated multi-scale modeling was given, so as to realize a full set of theoretical system about aground-underground seamlessly integrated multi-lod modeling.Based on these studies, the software Geos3D-Mutil-LODM being developed to realize aground, terrain and underground three space seamlessly integrated multi-lod modeling, taking one district of Shenyang city as an example, experimental results showed that, the aground-underground seamlessly integrated multi-lod modeling method considering semantics proposed in this paper, can more fully utilize relative geosciences data for the seamlessly integrated modeling of aground, surface and underground objects, which provides a new approach and technology programs for multi-scale integrated modeling of geosciences.