Evaluation of Changes in the City Fabric Using Multispectral Multi-temporal Geospatial Data: Case Study of Milan, Italy

In recent decades the global effects of climate change have requested for a more sustainable approach in thinking and planning of our cities, making them more inclusive, safe and resilient. In terms of consumption of natural resources and pollution, cities are seen as entities with most significant impact to the natural environment. Strategic policies focused on tackling the challenges induced by climate change suggest in fact the necessity to start from the management and operating models of the cities themselves. This study illustrates an initial evaluation of parameters for purposes of urban generation studies using optical multi-spectral satellite imagery from Landsat-5, Landsat-8 and Sentinel-2 missions. The changes in land occupation and urban density are the first aspects chosen to be examined for the period 1985-2020. The focus was given on possible modifications occurred in occasion of Milano Expo 2015. The paper firstly explores the known best band combination for observation of urban fabric. Suggestions derived have then been calibrated with reference to ground truth data, while the image pairs over the 35 years span were then build with selected bands. Finally, all image pairs have been processed for Principal Component Analysis in order to identify possible "hot-spots" of significant changes. The results found on the image pair 2006-2015 have been explored in detail and checked upon official orthophotos. Monitoring of changes in urban fabric using multispectral optical imagery can provide valuable insights for further evaluation of single urban generation interventions. Such contributions could be considered in the processes of urban planning policies in a more systematic manner.