On the Use of Satellite Imagery and GIS Tools to Detect and Characterize the Urbanization around Heritage Sites: The Case Studies of the Catacombs of Mustafa Kamel in Alexandria, Egypt and the Aragonese Castle in Baia, Italy

The sustainable development of urban growth is a mandatory challenge to be addressed, as also highlighted in the Agenda 2030, and this requires suitable and sustainable planning strategies, as well as systematic and timely monitoring of urban expansion and its effects. In this context, satellite data (today also available free of charge) can provide both (i) historical time-series datasets, and (ii) timely updated information related to the current urban spatial structure and city edges, as well as parameters to assess urban features and their statistical characterization to better understand and manage the phenomenon. Nevertheless, it is important to highlight that the identification and mapping of urban areas is still today a complex challenge, due to the heterogeneities of materials, complexity of the features, etc. Our approach, herein adopted, addresses the challenges in using heterogeneous data from multiple data sources for change detection analysis to improve knowledge and monitoring of landscape over time with a specific focus on urban sprawl and land-use change around cultural properties and archaeological areas. Two significant test cases were selected: (i) one in Egypt, the Catacombs of Mustafa Kamel in Alexandria, and (ii) one in Italy, the Aragonese Castle in Baia–Naples. For both study areas, the changes in urban layers were identified over time from satellite data and investigated using spatial analytic tools to statistically characterize them. The results of this study showed that (i) the increase in urban areas is the main phenomenon around both heritage areas, (ii) this increase is sharper in developing countries (e.g., Egypt) than developed countries (e.g., Italy), (iii) the methodology herein adopted is suitable for both big and small urban changes as observed around the Catacombs of Mustafa Kamel and the Aragonese Castle.