A longstanding IDRC grantee Development Workshop combines satellite observations with old-fashioned grassroots data gathering to measure the impact of Angola’s rapidly growing slums on the environment. Since 2002, when decades of civil conflict ended, Angola has struggled to rebuild. Its planners are hampered, however, by a shortage of reliable data about their own country’s population and environment. If Angolan policymakers were to take effective measures to tackle urban destitution and environmental degradation, they needed a clear picture of the geographic distribution of slum dwellers and of their social and environmental circumstances. An ambitious IDRC-funded research project, aimed primarily at documenting the environmental impact of encroaching slums, has been painting this picture. The study was conducted from 2009 to 2011 by Development Workshop.