Monitoring Rapid Urbanisation with Imaging Radars Case Study: West Africa

Up to date urban mapping and population data are required by policy makers, economists and planners in the developing world, and particularly for cities in South Asia, Latin America and Africa, to enable informed decision making. For many of these regions (particularly in the tropics) the all-weather capability of spaceborne imaging radar could prove to be a reliable and systematic monitoring technique. The potential of repeat-pass ERS SAR data to synoptically monitor rapid urbanisation is demonstrated for Kumasi (Ghana) for the period December 1995 to February 1999. The results confirm the complexity of the relationship that exists between the radar cross section (RCS) and the built environment. As a result RCS are simulated using simple scattering models to study single bounce effects from roofs and double bounce effects from wall-ground structures. Initial results show that the RCS is strongly dependent on incidence angle for single-bounce scattering, and on look direction for double-bounce scattering suggesting that (i) ERS PRI data is most sensitive to roof structures, and (ii) Radarsat Fine Beam data is influenced more by wall-ground structures.