articles: Measurement of density gradients and space-filling in urban systems

New digital data sources for urban analysis are becoming available, which are far more disaggregate, comprehensive and frequently updated than those used hitherto in regional science. Urban theory in regional science has often been founded upon notions of settlement density that are not fully deliberated in theoretical terms, and which in practice are often shackled to inappropriate and overly coarse zonations. Clearer conception and better measurement of density and the related concept of space-filling are seen as central to applied analysis in regional science. In this spirit we probe the uncertain and ambiguous conception of urban `density' and space-filling, and illustrate how new data sources permit sensitivity analysis of measurements of these properties. We illustrate our arguments with an extensive, if necessarily preliminary, analysis of some characteristics of a large UK city, including a sensitivity analysis of density profiles and fractal measures.