Urban Detection, Delimitation and Morphology: Comparative Analysis of Selective “megacities”

Over the last 50 years, the world has faced an impressive growth of urban population. The walled city, close to the outside, an “island” for economic activities and population density within the rural land, has led to the spread of urban life and urban networks in almost all the territory. There was, as said Margalef (1999), “a topological inversion of the landscape”. The “urban” has gone from being an island in the ocean of rural land vastness, to represent the totally of the space in which are inserted natural and rural “systems”. New phenomena such as the fall of the fordist model of production, the spread of urbanization known as urban sprawl, and the change of scale of the metropolis, covering increasingly large regions, called "megalopolis" (Gottmann, 1961), have characterized the century. However there are no rigorous databases capable of measuring and evaluating the phenomenon of megacities and in general the process of urbanization in the contemporary world. The aim of this paper is to detect, identify and analyze the morphology of the megacities through remote sensing instruments as well as various indicators of landscape. To understand the structure of these heterogeneous landscapes called megacities, land consumption and spatial complexity needs to be quantified accurately. Remote sensing might be helpful in evaluating how the different land covers shape urban megaregions. The morphological landscape analysis allows establishing the analogies and the differences between patterns of cities and studying the symmetry, growth direction, linearity, complexity and compactness of the urban form. The main objective of this paper is to develop a new methodology to detect urbanized land of some megacities around the world (Tokyo, Mexico, Chicago, New York, London, Moscow, Sao Paulo and Shanghai) using Landsat 7 images.