The fractal or scaling perspective on progressively generated intra-urban clusters from street junctions

Abstract

The underlying complexity of urban space can be manifested by its fractal forms and scaling statistics. This paper examines these characteristics at the intra-urban scale through the lens of clustered street junctions (including road ends) in two Chinese metropolitan areas: Beijing and Shenzhen. We derived the cluster sets with Euclidean distance thresholds starting at 100 meters (m) and ending at 1000 m, and outlined each cluster using a concave-hull method to maintain their original irregular shapes. Within each delimited cluster, we examined four urban attributes: gross domestic product, number of street nodes, polygon area, and population. Our analysis revealed that power law distribution applied to almost every cluster set in terms of the four attributes, but varied from one attribute to another or from city to city, represented primarily by fluctuated power law exponents and ht-index values whose profiles along with the cluster growth can effectively characterize the urban structure. Additionally, we computed the spectrum of intra-urban scaling exponents with cluster size increments, contributing new insights into the allometric relationships between urban configuration and function.

Keywords

• spatial clustering
• urban structure
• urban function
• power law
• intra-urban scaling law