Study on function of urban land price on land spatial expansion based on the gravity model

Center of gravity is an important index to describe spatial distribution of geographical objects, it can exactly reflect spatial distribution and evolution characteristics of geographical elements. Using gravity model, this paper makes a detailed analysis on variation track about urban land price and land spatial expansion of Shijiazhuang from aspects of location, moving direction, distance of land price gravity center and land space gravity center from 1999 to 2008. Based on the comparative analysis of the relationship between two series of gravity centers, we draw conclusions about function of urban land price on land spatial expansion. Results show that there is close relationship between land price gravity center and land space gravity center, with adjacent location, same direction of movement and related convergence rate. The function of urban land price on land spatial expansion is mainly reflected in regulating spatial arrangement of urban land and guiding direction of urban land expansion.