Research On Urban Expansion And Driving Forces In The Three Provinces Of Northeast China Based On Google Earth Engine

The three provinces of Northeast China play a very important strategic role in safeguarding national defense security,industrial security,food security,energy security and ecological security.The research on urban expansion and driving forces in the three provinces of Northeast China can provide technical support and basis for formulating relevant policies for the revitalization and sustainable development of Northeast China.Based on GEE(Google Earth Engine),urban areas were extracted using annual mean night light data and threshold segmentation method.and makes monthly synthetic Landsat cloud removal images in different years.Multi-class feature data were constructed and optimized by SEa TH algorithm.The accuracy and effectiveness of the supervised classification algorithm are compared and verified.Based on the urban regions,the urban factors of the three provinces of Northeast China from 1989 to 2019 were extracted using the best classification algorithm.The spatial and temporal changes of construction land expansion in the three provinces of Northeast China and the provincial capitals are analyzed.Finally,an empirical study on the driving mechanism and driving forces of urban expansion in the three provinces of Northeast China is conducted.The main results are as follows:(1)The annual average nighttime light data of NPP/VIIRS were produced and the urban areas were extracted using threshold segmentation method.Six Landsat cloud removal monthly composite images of different years were made.On the basis of the original spectral features,a total of 20 feature data of index,texture and terrain are constructed.SEa TH algorithm was used to optimize all the feature data,and the number of features was reduced to 12,which reduced the operating load and improved the extraction accuracy.By comparing the extraction accuracy and effect of random forest algorithm,classification regression tree algorithm and support vector machine algorithmin in extracting urban construction land,it is concluded that random forest algorithm has the highest extraction accuracy and the best effect.The random forest algorithm is used to extract construction land in urban areas in the three provinces of Northeast China.The water body was extracted by using Otsu algorithm combined with Modified Normalized Difference Water Index.The average overall accuracy of urban construction land and water element extraction is 95.9%,and the average Kappa coefficient is 0.92(2)Based on the spatial and temporal changes of the expansion area,center of gravity movement,expansion speed,expansion intensity,expansion proportion and expansion direction of the construction land in the three provinces of Northeast China and the three provincial capitals from 1989 to 2019,it can be seen that the total area of urban construction land in the three provinces of Northeast China has kept growing in the past 30 years.From 1989 to 2019,the area of construction land in all cities expanded by 49.07%,2.25 times in Shenyang,2.09 times in Changchun and 1.8 times in Harbin.From 2007 to 2013,the urban construction land expansion area in the three provinces of Northeast China was the largest.From 1989 to 2019,the total construction land expansion area of Shenyang was larger than that of Changchun and Harbin.From 1989 to 2019,the center of gravity of shenyang's main city moved to the southwest,the center of gravity of changchun's main city shifted to the southeast,the center of gravity of Harbin's main city shifted to the northwest.The cities in the three provinces of Northeast China as a whole are slow expansion type from 1989 to2019.Shenyang was slow expansion type from 2001 to 2007,Changchun and Harbin were slow expansion type from 2007 to 2013,and Shenyang,Changchun and Harbin were slow expansion type in other times.From 1989 to 2019,the main urban area of Shenyang expands mainly to the west and south,the main urban area of Changchun expands all around,and the main urban area of Harbin expands mainly to the northwest.According to the elasticity coefficient of urban construction land expansion in Shenyang,Changchun and Harbin,the expansion rate of construction land in the capital cities of the three provinces of Northeast China is faster than the population growth rate.(3)The driving mechanism of urban construction land expansion in the three provinces of Northeast China includes many factors.Based on the empirical analysis of the driving force and driving force of urban construction land expansion,such as thrust,support force,elasticity and resistance,it can be seen that economic factors,population factors and traffic factors are the main factors that promote the expansion of urban construction land,these factors play a decisive role in the expansion of urban construction land.Natural and administrative factors provide convenient conditions for the expansion of urban construction land.The development zone construction,new district construction and university city construction are the driving forces for the expansion of urban construction land in different areas of some large city.To some extent,the protection of ecological environment and cultural sites has hindered the expansion of urban construction land.By constructing the driving index system of urban construction land expansion,the driving force equation of urban construction land expansion is established by stepwise regression analysis.In view of the present situation and existing problems of the cities in the three provinces of Northeast China,this paper puts forward some suggestions for the future development of the cities in the three provinces of Northeast China.