Polynuclearity as a Spatial Measure of Urban Sprawl: Testing the Percentiles Approach

Polynuclearity and polycentricity are spatial phenomena which overlap each other in the context of urban sprawl, and this sometimes hinders the possibility of clearly distinguishing the two. Hence, the basic goal of the article is to indicate the differences between polycentricity and polynuclearity as well as their conceptualization and operationalization as urban sprawl features. The article indicates that the main differences between polycentricity and polynuclearity boil down to functional connections. However, empirical exemplification was made in relation to the agglomeration of Cracow, Poland using an urban morphology approach based on 1 km 2 square grids. Among the conclusions, it can be found that the identification of the central core is an important stage of research. If at least two cores appear then polynuclearity is identified and then polycentricity can be further identified. Testing of four mathematical approaches to identifying the central core showed that the most accurate results are given by the 95th percentile, i.e., the grids within the 95th percentile of building density qualify for the central core. It is also necessary to remove grids with extremely high building density from the analyses.