Realization of Multi-Scale Building Models for Cost-Effective Web 3D GIS Applications

摘要

For Web 3D GIS applications based on photo-realistic city models, the efficiency of visualization is crucial because it normally contains a large data volume of digital terrain models (DTM), textured building models, high-resolution ortho-images, city furniture, trees, and many kinds of thematic coverage. The cost to create a photo-realistic city model would be huge due a lot of effort and data required in geometric building modelling, texture mapping, thematic map compilation, DTM, ortho-image generation, etc. In the meantime, for the purpose of integrating Web 3D GIS applications based on cyber city, a cost-effective data model is critical. Since the 3D building model is the most important feature in 3D GIS applications, the multi-scale building models similar to CityGML are utilized and extended in the paper. In the meantime, in order to improve its efficiency in building modelling and suitability for certain applications, the level of detail (LOD) that applies to a building is defined according to its location and significance to the application. In this study, the multi-scale building modelling was performed based on a 2D digital topographic map with a scale of 1:1000 that contains detailed building polygons and number of stories for each building. For the purpose of location-based service applications, the extended building models were categorized into the following five LODs and named according to their appearance and cost. These are: (1) the block model, which has a flat rooftop with vertical walls but no texture, (2) the generic texture model, whose texture is automatically assigned by its attributes, (3) the economic model, which is a polyhedral building model with real texture, (4) the luxury model, which is extended from the economic model with more detailed facade information, and (5) the architectural model that is used for landmark buildings with real texture, complex facade, and interior geometry. For the realization of multi-scale building model and Web 3D GIS applications, the INet Universe 4D~(PilotGaea) platform is utilized in the paper. Some case studies in multi-scale building modelling and future applications based on the proposed scheme are introduced.