Time-space Development And Influence Network Analysis Of Natural Cities Based On Nighttime Lighting Data

With the continuous deepening of urban research and accurate disclosure of regional differences in urban development,the importance of objectively reflecting the changes in the spatial and temporal attributes of urban development has gradually attracted the attention of scholars and has become a new direction of urban research.However,due to the limited timeliness of traditional urban research data,the lack of space-time attributes and the limitations of administrative divisions,the existing research is still difficult to truly reflect the actual development differences of real “city”.Based on the DMSP/OLS nighttime lighting data,the HT-Breaks method based on fractal theory is used to extract the objective region of human activity--the natural city as the research subject.From a new perspective,it analyzes the spatial and temporal changes of China's urban development and the spatial interaction.Research conclusion is as follows:(1)It is feasible and reasonable to extract natural cities based on DMSP/OLS data by using HT-Breaks method.The HT-Breaks method was used to extract 216,258,and 304 natural cities in 1992,2002,and 2012,respectively.The extraction of natural city area is larger than the area of the city's built-up area,which is less than the area under the jurisdiction of the city.The results of the extraction is feasible and rationality.(2)The area of natural cities and the characteristics of lighting attributes show a gradual increase,but the changes have obvious timeliness.The area of natural city is inversely proportional to the quantity.The larger the area,the smaller the number,the more obvious the difference in area,and the change is time-based.In the past 20 years,natural cities with an area of >1000 square kilometers have expanded in space and adjacent natural cities,with the largest growth rate.The growth rate from 1992 to 2002 was 17.73%,much lower than 40.15% from 2002 to 2012;The area with the largest area of 100~200 square kilometers increased the fastest,reaching 50.00%,and the growth rate of area and area between 1992 and 2002 was 27.27% and 27.65%,respectively,which were greater than 17.86% and 18.53% from 2002 to 2012.In the lighting properties,the number of brightness pixels and the total value of the light are steadily increasing.In 1992,the pixels with brightness <33 have an absolute advantage to reach 68.75%,the total value of the light reaches 45.38%,and the overall brightness of the natural city is low.After 20 years of development,the number of pixels is 21.37%(<33)<22.95%(33~43)< 26.23%(43~53)<29.44%(53~63)and the total value of lighting is 13.62%(<33)< 19.49%(33~43)<28.21%(43~53)<38.67%(53~63)are all stepwise increasing characteristics,and the overall brightness of natural cities is improved.The number of pixels with a light value of 43~53 and the total value of the light increased the most,reaching 359.52% and 358.75% respectively.The change rate from 1992 to 2002 was 105.12%,and 105.73% was slightly lower than the 121.28% and 119.21% of 53~63.However,between 2002 and 2012,it reached 124.03%,122.99% far exceeded 55.44% and 52.30% of 53~63.Each brightness pixel showed different development and change characteristics in two stages.(3)The natural city presents the modular development with Beijing-Tianjin,Yangtze River Delta and Pearl River Delta as the core,and the spatial distribution of fragmentation and accumulation in the key areas of Shanxi,Hebei,Henan,Shandong and Liaoning provinces.Characteristics,and there are significant differences in the phased development characteristics of different regions.The spatial expansion of natural urban areas and the development of lighting values are dynamically coordinated.The unbalanced development of 1992 gradually developed into a relatively coordinated equilibrium in 2012.The development area of the three major regions and the development of the radiation value of the lighting value are relatively high,but the development speed is inconsistent.The development of Xinjiang in the western region is good,the old industrial base in Northeast China has improved from the sluggish state,and the development situation in Shanxi Province is gradually languishing,and the economic transformation is imminent.(4)The natural city radiative power network and the attractive network show a distinct imbalance.The radiation network and the attracting network are dense in the east,sparse in the west,and the connection between the east and the west is poor.However,the radiation network has a high degree of complexity and strong stability,showing a rhomboid-like spatial structure.The attracting network was developed from a simple network centered on three major regions in 1992 to a complex network with multiple secondary cores in 2002 and 2012.The stability is enhanced and the spatial structure gradually changes from a triangular structure to a diamond-like structure.There is a significant difference between the attraction intensity of natural cities and the radiation intensity and degree.The difference in attraction is small,the change is not large,and the difference in radiation force is large and the change is large.However,both degrees of distribution show power-law distribution and have no scale,but with the passage of time,the scale-free characteristics are gradually weakened.