Big Data-Driven Analysis On Urban Activity Space Dynamics

In recent years,the focus of urban space research has gradually shifted from physical space and economic space to human-oriented urban activity space.With the city development and the improvement of transport system,urban spatial structure has undergone intense evolution,leading to constant changes in urban activity space.However,due to the lack of long-term individual activity data,“static”spatial-temporal analysis on activity patterns is the main focus of urban research,while “dynamic”sensing of urban activity space is relatively insufficient.In addition,existing research rarely considered the interaction between human spatial-temporal behavior and urban space.Human activity behaviors have impacts on urban activity space,while human behaviors are restricted by the urban structure.Through the study of the interaction between human behaviors and urban space,we can discover the evolution mechanism of urban space and enhance the understanding of the driving forces of urban development problems.Recently,multi-source spatial-temporal big data provide new approaches to sense human behaviors and quantitatively understand urban dynamics.Through the aggregation of individual features in the given spatial units,the perception from human to space can be realized.This paper conceptualizes a urban dynamic research model based on individual mobility data from the perspective of ”human(behavior)-space(structure)-city(development)”.On the basis of the proposed models,empirical research on urban activity space dynamics is conducted regarding different human behaviors.Specifically,the main work and contributions of this dissertation are as follows:1.Activity-travel features are extracted from individual travel trajectories.Individual activities are the basis of big data-driven urban space dynamics research.Two types of trajectory sequences,OD trajectory sequence and stay trajectory sequence are extracted from the individual trajectory data,which are used to identify activity features and commuting features,and construct activity space networks.2.An analytical model of residential dynamics is introduced,and spatial distribution and relocation patterns are empirically studied.The study focuses on the impact of surging housing prices and urban renewal policies on urban residents' housing choices.The results show that the pressure of housing costs has a significant impact on the distribution patterns of urban residents,forcing some commuters in city centers to relocate to suburban areas where living costs are lower.The relocated commuters prefer areas with better public transport accessibility to reduce commuting costs,such as the nearby areas of rail transit stations.The research provides a new analytical framework for refined urban research in big data era.The analysis findings provide new insights into further explorations of the impact of housing prices on urban development.3.An analytical model of jobs-housing dynamics is proposed,and empirical research on urban jobs-housing dynamics is carried out respectively at the individual level and city level.The study mainly explores the impact of rail transit development on urban jobs-housing relationships.Empirical research results indicate that the within-center commutes decreased,while the suburb-to-center and with-suburb commutes increased.Rail transit has a positive effect on improving employment accessibility and reducing commuting time of residential communities.Additionally,the opening of new rail transit lines has increased the distances between the individual's residences and workplaces by influencing individual relocations,exacerbating the separation of individual residences and workplaces.The study provides an important insight into the implementation of urban land development and transportation planning policies.4.An analytical model of activity space dynamics is designed,which delineates activity space from multiple dimensions respectively at the individual level and city level.An empirical study is conducted to analyze the changes in individual activity spaces and urban dynamics.The study mainly explores the impact of urban development on urban activity space.The results show that the activity intensity of the inner city is reduced while the intensity of suburban activities is enhanced,indicating the trend of activity space shifting from the inner city to suburbs.Along with the shift of activity space,people's activities increased slightly,while the range of activity space decreased.Additionally,the social interaction between low-income group and middle-income group has increased.The research results reveal that urban development influences individual's daily activities,which in turn changes the spatial structure of the whole city.The research indicates the significance of analyzing urban spatial dynamics from multiple levels and multiple dimensions using individual mobility data.The research contents and corresponding findings are interdependent,revealing the suburbanization trend of urban residents' activity space under the rapid urban development,and shed light on the process and mechanism of suburbanizaition through analysis on individual behaviors.Relocation behaviors show that urban residential space is shifting from the inner city to the suburbs with lower living cost.Commuting behaviors indicate the decentralization trend of employment space accompanying the residential suburbanization,which is reflected in the reduction of within-center commutes and the increase of suburb-to-center and within-suburb commutes.The analysis on activity space suggests that residents' daily activities have also shifted from the inner city to suburban areas.The reduction of affordable housing in the inner city and the expansion of rail transit will further accelerate the suburbanization of urban activity space.The above research results prove the feasibility and effectiveness of big data-driven research on urban activity space dynamics,and also reveal the significance of studying the evolution mechanism of urban activity space dynamics from the perspective of ”human(behavior)-space(structure)-city(development)”.