Multidisciplinary parameters for characterizing the 3D urban morphology: An overview based on the relational perspective

Intense and rapid urbanization is accompanied by expansion, with both planar and height changes in the urban landscape influencing urban energy consumption, local climate, and sustainable development. As essential components for quantitatively analyzing urban morphology, many indicators have been introduced and adopted for practical studies, presenting a complicated and pluralistic usage pattern, which may also weaken comparability and compatibility. Inspired by co-citation networks, we reviewed 92 relevant papers and summarized more than 200 indicators through network analysis to reveal and clarify the multiscale usage and interaction patterns of the indicators. With reference to theoretical and methodological sources, we divided the various indicators into five categories: landscape metrics, surface metrics, urban canopy parameters, building metrics, and other metrics. The indicators currently used have the following characteristics. First, numerous indicators exhibit a strong hierarchy and interconnected heterogeneity in the network. Some core indicators (e.g., mean height and percentage of landscape) occupy the central positions of the network, and node strength follows a power-law distribution. Second, different indicator types have distinct preferences for describing targets and terminology, and applying topics. Relatively few indicators have focused on vegetation, and the application of these indicators is primarily prevalent in the domain of environmental research. Third, the indicator network has a hybrid mesoscale structure combining core-periphery and community structures, which correspond to mainstream indicators governed by core and nascent indicators, respectively. Finally, we conclude that multidisciplinary indicators form an overlapping, developing, and integrated framework for quantifying the three-dimensional morphology of cities, which is expected to provide a systematic summary and reference for the indicators for urban morphology analysis.