Extraction Of Built-Up Areas In Guangdong-Hong Kong-Macao Greater Bay Area Based And Analysis Of Their Spatiotemporal Changes On Multi-Source Data

In the past 30 years,China's urbanization process has been in a period of rapid growth,and urban space expansion has been particularly significant.The built-up area is an important indicator of the level of urbanization of a city,and it is the starting point for understanding a city.The Guangdong-Hong Kong-Macao Greater Bay Area is a national strategy that General Secretary Xi Jinping personally planned,deployed and promoted.It is a new measure to promote the formation of a new pattern of comprehensive opening up in the new era.Inject new vitality into the country's economic development and reform and opening up.In this paper,the Guangdong-Hong Kong-Macao Greater Bay Area is used as the research area.Based on the city,Landsat images were used to preliminarily extract the built-up areas from 1993 to 2018 using the method of supervised classification of human-computer interaction,Using the mutation detection method to extract the built-up area of DMSP/OLS luminous images in 1993,2002,and 2011,and using the method of natural discontinuity and supervised classification results to extract the built-up area of NPP-VIIRS images in 2018.The built-up area extracted from the Landsat images intersects with the range of the built-up area extracted from DMSP/OLS images and NPP-VIIRS night light data to obtain the final built-up area.The expansion speed,expansion intensity,expansion dynamics,compactness,fractal dimension,and gravity center migration are selected from the city scale to analyze the expansion characteristics of built-up areas of each city and the differences between cities.The city's first degree,order-scale rule,city The indicators of connection strength,connection membership,and first place analysis analyzed the regional characteristics of the expansion of the Guangdong-Hong Kong-Macao Greater Bay Area.The following conclusions were obtained:(1)Landsat imagery is combined with DMSP/OLS and NPP-VIIRS noctilucent data to extract built-up areas.It not only takes advantage of the high spatial resolution of Landsat imagery to retain detailed information of urban built-up areas,but also combines the characteristics of the light images that are objective and closely related to human activities,which can reduce the influence of"same-spectrum foreign matter,same-spectrum foreign body",bare land,and small villages.At the same time,the built-up area is extracted by using the city as a unit,which fully takes into account the differences in urban development and improves the classification accuracy.The minimum overall accuracy of each city's supervision classification is 86.06%,and most overall accuracy is above 90%,and the classification accuracy is high.The correlation analysis of the built-up area extracted by this method and the statistical data of the built-up area R~2 is 0.965,which has a strong correlation,indicating that the extraction method of built-up area is feasible and reasonable.(2)The overall characteristics of the expansion of built-up areas in the Bay Area.The area of the Bay Area increased from 2343.53 km~2 in 1993 to 9143.33 km~2 in 2018,and the area of built-up areas increased by 6808.8 km~2,with an average annual increase of 272.35 km~2.Among them,the nine-year expansion in 2002-2011 is the fastest,the nine-year expansion in 1993-2002 is the middle,and the seven-year expansion in 2011-2018 is the slowest.The center of gravity of the Bay Area moved9599.14m to the northwest at 25.39°.Although the center of gravity of the Bay Area moved from 1993 to 2018,it was basically southwest of Guangzhou.Guangzhou was the center of gravity of the Bay Area built-up area at this stage.The compactness of the Bay Area is increasing-increasing-decreasing,and the fractal dimension is decreasing-decreasing-increasing,indicating that the expansion of the Bay Area was dominated by fill-type expansion from 1993 to 2011,and from 2011 to 2018 the epitaxial expansion mainly.(3)Expansion characteristics of built-up areas in various cities in the Bay Area.The expansion speeds of Guangzhou and Foshan have been very high,and the expansion speeds of Macau,Hong Kong and Zhuhai have been low.From 1993 to2018,Shenzhen,Foshan,Huizhou,Zhongshan,and Zhuhai,the five cities that started relatively late,exhibited the characteristics of first growth and then deceleration.Macau,Guangzhou,and Hong Kong,the three cities with earlier economic development,showed the first characteristics.The characteristics of speed increase after deceleration,the expansion of Dongguan and Zhaoqing has been accelerating,and the expansion of Jiangmen has been decelerating.The centers of gravity of the five regions of Macau,Dongguan,Foshan,Guangzhou,and Hong Kong are relatively short,while the centers of gravity of the six regions of Huizhou,Jiangmen,Shenzhen,Zhaoqing,Zhongshan,and Zhuhai are relatively far away.From 1993 to 2018,the overall compactness of the seven cities of Macau,Dongguan,Foshan,Guangzhou,Shenzhen,Hong Kong,and Zhongshan increased,while the overall compactness of the four cities of Huizhou,Jiangmen,Zhaoqing,and Zhuhai weakened.(4)The Bay Area development model and the interconnectedness of cities.The cities in the Guangdong-Hong Kong-Macao Greater Bay Area are subordinate in size.The first-ranked cities are not obvious enough,and the development of small and medium-sized cities in the region is relatively balanced,and there is no phenomenon that Dongguan or Guangzhou is the only city.With the continuous development of cities,the inter-city connections have been strengthened,and the total strength of each city's external contacts has continued to increase.From 2002 onwards,the total strength of Guangzhou's external contacts has always ranked first.At the same time,high-value areas with Guangzhou as the core,Foshan and Dongguan as the sub-cores have gradually formed,while Hong Kong and Macau are in the low-value area with the total strength of external contacts.From the first contact direction,Zhaoqing-Foshan-Jiangmen,Guangzhou-Zhongshan-Zhuhai-Macao,Dongguan,Shenzhen,Huizhou,and Hong Kong have formed three small city groups.Guangzhou,as the first contact direction of Zhaoqing and Foshan,has The three small city clusters are linked into a whole.