Analysis Of Space Structure Development Of Shijiazhuang City Based On Nighttime Light Data

Changes in urban spatial structures have important links with the development of human socioeconomic activities and the acceleration of urbanization processes.Based on different spatial scale changes mainly include: urban external morphology of the construction zone,the differentiation and reorganization of urban centers in the city.Changes in urban build areas are mainly based on urban area,and specific can be reflected in the variations in various types of urban parts.If the city expansion does not use urban development plan to guide blindly expand,it will cause great damage to human production,urban transport,and natural environment.Therefore,accurately and efficiently controlling the changes in urban external morphology and social economic attributes,it can provide data support to the city's future planning.on the other hand,compared to the change in the area of urban construction,the changes in urban centers is more complicated.Its main changes are the center transition into multi-center.The formation of multi-center urban structures can provide a broader sustainable platform for the development of urban economic at present,to alleviate the pressure of population,road traffic,and build a more distinctive city image.Accurate assessment of the development status of urban centers,it can provide reliable feedback to the development of future planning.This paper summarizes the research status of domestic and foreign research by analyzing,using NPP-VIIRS nighttime light data as the main data source to carry out changes in urban spatial structural.The main contents are as follows:(1)Urban construction area extraction methodThis paper combines NPP-VIIRS nighttime light data with LANDSAT8 OLI data to construct a construction-calibrated city nighttime light index(BANUI index),through the marked watershed algorithm to split the urban external form,and conduct an extraction of urban construction zones.Using Shijiazhuang City Land Use Data,Relevant Statistics,and Confused Matrices Verified the extraction results,The results show that among the four extraction methods,the accuracy of urban built-up area extracted from the union of BANUI65 and BANUI43 is the highest,and the accuracy of urban built-up area extracted from NPP-VIIRS nighttime light is the lowest.(2)Urban center identification methodBased on multi period NPP-VIIRS nighttime light data,avoids the influence of administrative boundary caused by using discrete data.The local contour tree algorithm combined with layered color method is used to identify all kinds of urban spatial center structure,which makes the analysis results of color shading visualization,and increases the three-dimensional sense and identifiability.The starting equivalent line value is determined by the construction site boundary lighting brightness,and the correctness of the research results is further ensured.Compared to traditional urban center recognition methods,this method can not only identify the specific location of the city,but also determine the boundary range.(3)Urban spatial structure analysis modelIn this paper,the analysis of urban spatial structure is carried out from two aspects of urban built-up area and urban center change.The expansion of urban built-up area is described by the change of scale characteristics and expansion space evolution.The expansion intensity index and night light intensity index are used to describe the change of scale characteristics.The standard deviation ellipse method is used to describe the expansion space evolution.Through the change of space hierarchical structure,urban center quantitative analysis describe the evolution of the interior center of the city,describe the variation of space hierarchical changes in six different cities,using attribute information such as compactness,area change,etc..Finally,Shijiazhuang city is taken as an example for specific analysis.The conclusions are as follows:From 2013 to 2019,the urban spatial structure of Shijiazhuang city changes significantly,in which the urban built-up area is on the rise as a whole,the spatial distribution is "northwest southeast" distribution,and the expansion direction and gravity center movement direction are mainly in the East,showing the trend of southeast and northeast expansion.There are many city centers in the city,and the structure of the central city is stable.There are also city centers in other counties and cities.The urban pattern of "Three groups on both sides of one river" has been basically formed,and all kinds of change characteristics are consistent with the urban development planning of Shijiazhuang.