Diffusion in a Central Place System

Abstract

Diffusion in a Central Place SystemIn spatial diffusion theory there are two important ideas about the spread of things that are advanced as process explanations of geographical patterns.The most frequently mentioned process is contagious spread, producing the "neighborhood effect" of clustered growth.Hagerstrand developed an operational model to simulate this process of individuals passing a message to their neighbors.'Although many non-spatial modifications have been appended to Hagerstrand's original contribution, the spatial process of clustered growth is the essential idea.Tobler has recently suggested procedures for further development of this model.2Tobler's contribution calls attention to the relationship between clustered growth and the mechanics of the "innovation wave," a connection which the Hagerstrand simulation model never established.There is little doubt that contagious growth and diffusion waves are important in distribution genesis.A second major idea, also brought to light largely due to Hagerstrand's work, is that things diffuse downward through the central place hierarchy?Hagerstrand writes:A closer analysis shows that the spread along the initial "frontier" is led through the urban hierarchy.The point of introduction in a new country is its primate city; sometimes some other metropolis.Then centers next in rank follow.Soon, however, this order is broken up and replaced by one where the neighborhood effect dominates over the pure size succession.