Characteristics and Driving Mechanism of Urban Space Expansion in Urumqi

  Objectives  With the rapid advancement of urbanization, the study of urban space expansion has become a hot spot in urban development research.

  Methods  Based on statistical yearbook data, land use status remote sensing monitoring data, and DMSP(defense meteorological satellite program)/OLS(operational linescan system) night light data, we can extract the urban construction land and calculate the change of area. In order to obtain the expansion types and expansion direction of Urumqi from 2000 to 2018, we use the method of convex shell to recognise the expansion types, and use the methods of centroid shift and the standard deviation ellipse to judgment the direction of Urumqi's expansion.

  Results  The results show that Urumqi is middle speed expansion mode from 2000 to 2006, high-speed expansion mode from 2007 to 2013, and fast expansion mode from 2014 to 2018. The recognition results of the method of convex shell show that the expansion types of Urumqi from 2000 to 2018 are all filled. The direction of Urumqi's expansion judged by the method of centroid shift is that Urumqi's center of mass shifted to the southwest from 2000 to 2006, the center of mass continued to shift toward the southwest from 2007 to 2013, the center of mass shifte toward the northeast from 2014 to 2018.The verification results by the method of standard deviation ellipse show that Urumqi expand along the northwest-southeast direction from 2000 to 2006, expand along the southwest-northeast direction from 2007 to 2013, continued to expand along the southwest-northeast direction from 2014 to 2018. The direction expands between methods of centroid shift and standard deviation ellipse is substantially the same.

  Conclusions  The driving mechanism of Urumqi's urban expansion is subject to many factors. The interaction of multiple factors, while promoting urban development, also causes the spatial and temporal differentiation of urban expansion.