Search

Identifying urban boundaries involves analysing both the functional and the morphological aspects of urban systems. In this paper, we adopt a purely morphological approach and compare three methods for the morphological delineation of cities. Each method avoids using any predefined quantified threshold (size, distance, built density, etc.) to detect crucial discontinuities in space. The first method identifies Natural Cities by clustering points. The other two are the fractal-based MorphoLim method and the Hierarchical Percolation; both involve transforming the data using a step-by-step dilation process. The three methods are critically compared and illustrated by applications to theoretical urban patterns. We further apply each method to the urban agglomeration of Brussels, the Belgian capital, using different data (building footprints, building centroids and street nodes) and considering two study areas, namely the former province of Brabant and the entire country of Belgium. The results show that it is impossible to draw an unambiguous morphological boundary for an urban agglomeration. Consequently, it is crucial to relate the data used, the size of the study area and the method chosen to the objectives of the delineation. [ABSTRACT FROM AUTHOR]

In this paper we explore further the use of fractal dimensions by comparing values for built-up spaces and values for road networks, both being estimated by the same method. This is done in an attempt to explain the differences theoretically and empirically, and to show how far both indices are complementary and useful in urban planning. Empirical analyses are performed at the scale of the townships within the urban region of Antwerp (Belgium). Fractal dimensions, curves of scaling behavior, and concordance analyses are computed and their usefulness explained. We conclude that both dimensions translate subtly different realities and that they should be used with caution in morphological analyses: the fractal dimension for built-up spaces indicates how uniformly buildings fill space when zooming to ever finer scales, while the fractal dimension for networks indicates the extent to which street segments are distributed more or less uniformly in the study area. The two are not the same, as roads can serve spaces that are not built up. [ABSTRACT FROM AUTHOR]