To analyze the relationships between urban expansion and the changes in the SUHI more deeply, we drew the centroid transfer path for Nanjing city during the past decade. The spatial centroid is an important indicator that describes the spatial distribution of a geographic object and has often been used to study city evolution and changes in the SUHI.47,48 The spatial centroid is a comprehensive response to the SUHI and built-up region distribution characteristics. Analyzing the centroid transfer path not only reveals the spatial expansion of Nanjing but also illustrates the development of the city’s effect on the development of the SUHI. Zhang et al.49 provided a theoretical definition and a formula for the spatial centroid for a single geographic object using vector landscape theory. To further analyze the shifts in the distance and direction of the centroid, Dong et al.50 used three variables: the spatial centroid coordinates, the shift distance, and the angle of the spatial centroid. The spatial centroid coordinates can be expressed as follows: Display Formula
(5)and Display Formula
(6)where and are the mean spatial centroid coordinates of a geographic object; is the area of portion of the object; and and are the geometric centroids of the ’th portion. The shift distance and the shift angle of the spatial centroid are computed as follows: Display Formula
(7)and Display Formula
(8)where is the shift distance of the spatial centroid from time to and is the shift angle of the spatial centroid from time to .