One factor that must be considered in thinking about urban applications of remote sensing is that there are often better sources of the same information that can be obtained more economically, particularly for cities in developed countries. For example, tracing the advancing line of urban settlement in industrialized countries can be accomplished with local government records of building permits, the extension of utilities, and the construction of roads. This is not always the case in developing countries, however. Since urban settlement in developing countries is often informal, municipal records, when available, usually cannot keep pace with changes in the extent of settlements. Mapping the advancing line of settlement with remote sensing is thus more useful in these settings. Yet even though this information may improve our understanding of the pace of urban expansion, it often does not improve our capacity to manage urban environments, since informal settlement on the fringes of urban areas in developing countries is generally not subject to policy intervention.