ABSTRACT
Urban places may be broadly defined as settlements where most people live and work. Human beings worldwide tend to cluster in spatially limited habitats occupying less than 5% of the world’s land area. The density of infrastructure — or “urbanness” — can be viewed as a continuum ranging from wilderness at one extreme to central business districts at the other extreme (Weeks, 2004). Because of their key role in sustaining human civilization and their impact on the environment, there is substantial interest in global mapping of human settlements and updating such maps on a routine basis.
