Analysis of urban elements orientations to characterize the spatial extension of the foundation of the Roman city of Amida

Abstract. The structure of the historical center of the city of Diyarbakır is largely inherited from the Roman city of Amida, through numerous testimonies still present in certain urban elements, such as buildings or cadastral parcels. The detailed analysis of the orientation of these urban elements in the current urban plan of Diyarbakır can contribute in particular to a better understanding of the different eras of foundation of the city of Amida and their spatial extensions. This research proposes to compare two methods of extraction of orientations from urban elements of the city of Diyarbakır. First, historians carried out a manual survey of the orientations from an aerial photograph, which made it possible to bring out two frames corresponding to two eras of the founding of the Roman city of Amida. These orientations were then compared with those extracted automatically from the geographic databases of cadastral parcels and built-up urban elements captured at a large scale. If the results obtained with the two methods converge, they also show differences, both on the orientation values and on the spatial extension of the two frames observed. These differences may contradict the initial observations, but are also sources of new perspectives of research on the spatial extension of the different periods of foundation of the Roman city of Amida. Finally, the results of this research tend to show that the two approaches prove to be complementary in detecting ancient urban structures in a contemporary city plan.