Satellite images are significant in monitoring urban development. This application involves the acquisition of satellite images of the same area at different periods. Continuous acquisition at different time intervals ultimately builds a time series database of the area. The images are then interpreted to identify changes, in this case development in building structures. Such an application is critical to advance and support government and environmental programmes such as social upliftment and climate change, and monitoring service-delivery projects, such as the constriction of low-cost housing.
Acquiring imagery of the same area over time provides us with data required to study changes in human settlements. Some of the changes that we can observe currently are settlement expansion (informal and formal), decline or conversion of informal into a township and development of new informal settlements. SANSA and the National Department of Human Settlement have conducted informal settlement change detection between 2006 and 2011. The results show that even though there were a number of informal settlements that were upgraded (in-situ or relocation), new informal settlement developments and expansion were observed during this period.