Polymorphic Representation Method Of Urban Elevation Model For Urban Three-dimensional Morphology Analysis

Urban morphology has always been a research hotspot in geography and related fields,and it is also an important factor affecting the process of urbanization,urban ecological environment,and economic activities.The spatial evolution of urban morphology not only occurs on a two-dimensional plane,but also occurs in a threedimensional space.With the three-dimensional development of the modern city,the importance of three-dimensional urban morphology is increasing,and a growing number of researchers pay attention to the representation and analysis of threedimensional urban morphology.The traditional three-dimensional urban morphology representation method based on entity object model has the limitation that it cannot take urban natural terrain surface into account.The data model based on elevation can represent the three-dimensional urban morphology composed of urban buildings and the ground surface in a unified way,which can more completely represent the threedimensional urban morphology.At present,the data model based on elevation has not received enough attention in the related research fields.The main reason is that the existing data models are relatively few and the representation modes are relatively simple,which is difficult to meet the complex analysis needs of the three-dimensional urban morphology.Therefore,it is necessary to carry out a scientific and systematic cognition of the three-dimensional urban morphology representation model based on elevation,and a research on its multimodal representation methods,forming a more diversified data model to support the analysis of three-dimensional urban morphology for different research needs.To meet the main requirements of urban three-dimensional morphological analysis,this paper proposes the concept of urban elevation model,which uses elevation to characterize the urban morphology composed of buildings and the natural surface of the city.This paper first systematically summarizes the conceptual framework of urban elevation model.Secondly,based on the conceptual framework,the multimodal representation methods of urban elevation model are proposed,and multimodal urban elevation models are constructed in the experimental plots.Based on the multimodal urban elevation models,the diverse empirical application research on the threedimensional morphological analysis of the city is carried out.The main contents and research results obtained in this paper are as follows:(1)The conceptual framework of urban elevation model is systematically explained.From the perspective of urban three-dimensional morphological spatial recognition,the constituent elements of the three-dimensional urban morphology are analyzed.Establish the definition of urban elevation model,summarize the connotation and extension of urban elevation model,and form a relatively complete concept framework of urban elevation model.The main research needs of urban elevation model for three-dimensional urban morphological analysis are summarized.(2)The construction of the representation method system of the polymorphic city elevation model is realized.From three levels of information sources,information processing methods and information carrying forms,the multimodal representation methods of urban elevation models are systematically studied.(3)Application and evaluation of multimodal urban elevation models.In the Xiamen Island experimental plot,based on the constructed multimodal urban elevation models,the application analysis and research of the three-dimensional urban morphology is carried out,including the analysis of the urban skyline,the analysis of the horizontal sections of the city,the extraction of the center of gravity of the threedimensional morphology and the analysis of the hierarchical structure of the urban morphology.Four application cases prove the applicability of the multimodal urban elevation model.In addition,the evaluation and analysis of multimodal urban elevation models also clarifies the characteristics and differences between urban elevation models based on different data structures.This study puts forward a multimodal representation method of urban elevation model for the three-dimensional analysis of urban morphology,which is an important supplement to the existing three-dimensional representation models of urban morphology.The multimodal urban elevation model has a certain application value for the analysis of the three-dimensional urban morphology and related research.The application analysis methods based on the multimodal urban elevation models are also a useful exploration and expansion of the urban morphological analysis.