GIS-based study on spatial growth of bi-polar with corridor in the Baltimore-Washington region in the USA

The sprawl process in the metropolitan area of the Baltimore-Washington is a typical Bi-polar growing process among corridors. This paper studies the urbanization of Baltimore-Washington region within 200 years. By using the GIS software Mapinfo7.0, we gained the ratio changes of urbanized area to non-urbanized area and the radii of incircle and circumcircle of two regions. Then we took the former as integrated study and the latter as contrastive study. We find that the metropolitan growth has a 30-40-year cycle phenomenon. Both core growth and corridor growth form the urban expansion of Baltimore and Washington, but each of them has different rates and characteristics. This process can be described as "point-line-net-surface growth model". And the urban growth of Baltimore is better than Washington. Usually, traditional studies of spatial sprawls of Bi-polar of growth with Corridor Structures take the Bi-polar of growth with Corridor Structures as a whole to study the expanding process, while this paper tries to reveal the law of the spatial growth of Bi-polar of growth with Corridor Structures by contrasting the growths of cores, the growths of corridors and the growths of core and corridor in two regions. Moreover, this study is built on the GIS platform and takes the GIS as a research base by using GIS software to access and processing of remote sensing data. At the same time, the paper uses the ecological processes model to carry out quantitative study to deepen its understanding on the Bi-polar growing with corridors structure, and this will conducive to scientific urban and regional planning.