Spot5 Quantifies Rapid Urban Change

The rapidity of urban dymanics has a significant impact on the spatial patterns associated with the growth and expansion of metropolitan areas. High resolution satellite imagery with equally rapid image update capabilities offers significant potential for helping to maintain the accuracy of associated cadastre, municipal subdivision boundaries, voting districts and enumeration areas (population census zones) in these urban areas. This paper demonstrates the value of combining new high resolution satellite image sensors such as Spot5 with enumeration areas (EA’s) in a geographical information system to identify urban change as well as quantifying the type of change in a metropolitan area in South Africa. Spot 5 images were recorded during August 2002 for the Pretoria metropolitan area in South Africa in all three modes (10m, 5m & 2.5m). All of these images were combined with enumeration areas (EA’s) from the October 2001 Population and Housing Census in South Africa, as produced by Statistics South Africa. To map urban growth and model associated change, the urban EA’s (consisting of appoximately 200 households per EA) were selected as a base framework around which change would be determined. As a next step, all new areas of growth were assessed in terms of using SPOT5 for more quantitative house counts in order to demarcate new EA’s boundaries. The results indicate that both the Spot5 Colour (10m) and Panchromatic (5m) are sufficient to detect and classify urban growth, while the colour enhanced Supermode and the Supermode can be used with confidence to detect individual house structures in formal residential areas and to use this to demarcate new EA’s. * Corresponding author