A Quantitative Research Of China Megacity Morphology Based On Urban Spatial Big Data

Megacities,as an important flow place of the urban population in China,generally account for 70%in urbanization rate of its permanent resident population,taking the lead in entering the era of stock renewal under the dual background of the new normal of economic development and entering the middle and late stages of urbanization of China.As an advantageous geographical location and the core economic pattern,the megacities are ahead small,medium and large cities in terms of population size and spatial construction of China.Moreover,along with the development of digital technology and artificial intelligence,the basic data used in urban morphology research are changing from a small amount to an unprecedented large quantity,from single-dimensional to multi-dimensional complexity,and from low-resolution to high-resolution precision.Although multi-dimensional urban spatial big data are flourishing in practical application,the theory of urban morphology has not completely surmounted the barriers of empiricism and human brain judgment,and big data still remains in the level of supporting urban morphology analysis and supporting empirical theory.Combined with the development background and technical background,it studies and focuses on the form of China's megacities and builds a hierarchical urban spatial big data platform for megacity morphology based on urban spatial big data of architectural precision.Relying on the platform database and analysis module,quantitative definition,measurement and analysis are carried out,and the surface regular features of megacity morphology are summarized.From the perspective of overall space,the megacity morphology is recognized,and the basic flour,clusters,depressions,green wedges and corridors in the megacity f morphology are discovered.From the perspective of reduced space,a prototype paradigm is proposed to describe the urban morphology,and the prototype concept is defined theoretically.On the data platform,further quantitative definition and measurement analysis of prototype elements are carried out so as to induce the deep rules of megacity morphology prototype.Finally,the theory of urban morphology prototype and its topological model are constructed,the third-order prototype of megacity morphology and its subtypes are discussed,and the essential connotation and composing mechanism are explored.Two main innovation points of this paper are summarized as follows:1.Based on the research of the spatial database of China's megacities,the five elements of megacity morphology are precisely defined and analyzed.Based on real high-precision urban spatial big data,spatial indexes such as spatial intensity,density,height,boundary,center of gravity,network,texture and other morphological indexes under the surface morphology of megacities are quantitatively analyzed,and the characteristic laws of intensity multi-level attenuation,height multi-level attenuation,network multi-level attenuation,texture multi-level growth from the center of gravity to the boundary of megacity morphology are summarized,and then the five element characteristics of continuous plane of base surface,cluster high-value bulge,depression low-value depression,green wedge penetration and corridor connection are discovered in megacity morphology.In addition to the traditional urban form green wedge and corridor elements,the basic surface,cluster and depression elements are added.Based on the spatial intensity index of street areas in the urban spatial big data,the five elements of megacity morphology are precisely defined,and the third-order hierarchical characteristics,spatial distribution characteristics and quantitative structure characteristics of the five elements are measured and analyzed.2.It constructs the prototype theory of megacity morphology in urban morphology,and enriches the prototype theory system of international city morphology.The theory puts forward that the prototype of megacity has five elements,three levels and duality.The five elements are base surface,cluster,depression,green wedge and corridor.From low to high,the three levels show the three-level order of the base surface of the continuous area,the base surface of the main urban area and the base surface of the central area,the three-level order of the new town cluster group,the main city cluster group and the central cluster group,the three-level order of the edge depression,the main city depression and the central depression,the three-level order of the green wedge,the agriculture and forestry green wedge and the landscape green wedge,and the three-level order of the main road corridor,the track corridor and the fast corridor.Duality is divided into four unity of opposites:implicit and explicit,virtual and actual,internal and external,concave and convex.It sums up rules of the prototype of megacities in terms of shape,element,grade,structure and mode.It initially constructs the initial prototype model and fractal iteration model of urban morphology with self-similarity and isomorphism characteristics,and induces three prototype subtypes models derived from megacity morphology.