Understanding uneven urban expansion with natural cities using open data

The last several decades have witnessed a rapid yet uneven urban expansion in developing countries. The existing studies rely heavily on official statistical yearbooks and remote sensing images. However, the former data sources have been criticized due to its non-objectivity and low quality, while the latter is labor and cost consuming in most cases. Recent efforts made by fractal analyses provide alternatives to scrutinize the corresponding “natural urban area”. In our proposed framework, the dynamics of internal urban contexts is reflected in a quasi-real-time manner using emerging new data and the expansion is a fractal concept instead of an absolute one based on the conventional Euclidean method. We then evaluate the magnitude and pattern of natural cities and their expansion in size and space. It turns out that the spatial expansion rate of official cities (OCs) in our study area China has been largely underestimated when compared with the results of natural cities (NCs). The perspective of NCs also provides a novel way to understanding the quality of uneven urban expansion. We detail our analysis for the 23 urban agglomerations in China, especially paying more attention to the three most dominating urban agglomerations of China: Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD). The findings from the OC method are not consistent with the NC method. The distinctions may arise from the definition of a city, and the bottom-up NC method contributes to our comprehensive understanding of uneven urban expansion

Prioritizing future funding and construction of the planned high-speed rail corridors of China – According to regional structure and urban land development potential indices

Abstract(#br)This paper proposes two types of indices to prioritize the future funding and construction of the planned high-speed rail (HSR) corridors of China. The first index is the regional structure index that evaluates the performance of an HSR corridor from the perspective of spatial connectivity and accessibility, and it consists of regional structure factors (e.g., corridor length and buffer area) and coverage factors (e.g., the total number of HSR stations, cities, and people within the service domain of the HSR corridor). The second index is the urban land development potential index that assesses an HSR corridor depending on the corridor’s potential effect on the promotion of urban land development. Following China’s latest national railway network planning proposal, planned HSR corridors are prioritized using these two indices. The rankings obtained according to these two indices are presented and compared in this paper. The prioritization of results is then used to suggest patterns of future funding and construction for China’s HSR corridors and, further, to suggest potential implications for HSR planning and development in other countries