The Geographical Analysis of Megacities Through Changes in Their Individual Urban Objects

This research utilized global coverage, annual, high-quality land cover time-series data to explore the urban growth process in the core area, and in several buffer zones, of Beijing, Guangzhou, Shanghai, and Tokyo. We developed a conceptual model in which growth is characterized at the per-object level by four active growth events: introduction, establishment, dispersal, and coalescence, with a fifth inactivity event, stability. We developed a rule-base which allowed the direct measurement of establishment, dispersal and coalescence from observed inter-annual changes in the urban objects over time. By aggregating the object-level events to the landscape level we showed that these three events generally followed a synchronous temporal trend in terms of magnitude within the core area and within each buffer zone. There was no evidence for a logical sequence of events through time. The identified events dominated alternately over time, although synchronicity in magnitude far outweighed any differences in proportion between them. This points to a single underlying urbanization process: urban growth with a specific dynamic rate. Interestingly, synchronicity was not generally observed between the core and buffer zones. This proposed object-based method provides insights into the underlying urban growth process and could be used to build new urban growth models.