Towards an operative use of remote sensing for exploring the past using satellite data: The case study of Hierapolis (Turkey)

摘要

This paper is focused on the presentation and discussion of an object oriented approach, applied to the Hierapolisud(Turkey) site, to automatically detect the subtle features linked to buried archaeological remains. The data processingudis applied twice: (i) first, globally at the whole image and, (ii) second, at the significant subsets identifiedudby global analysis, in order to refine the previously obtained categorization. Object oriented approaches are usuallyudbased on two main steps: i) first the segmentation, ii) then the classification. Herein, we first performed theudunsupervised classification step and, then, the segmentation. This choice is given by the specificity of archaeologicaludissue, in particular: (i) the subtle features/targets to be identified are partially or totally unknown and characterizedudby a very small spectral separability from the background, and therefore (ii) the discriminationudbetween archaeological class and substrates likely suffers significant confusion. To cope with these issues, theudfirst step is based on an unsupervised classification, which provides a first ‘rough’ categorization of pixels; theudsecond step, based on the segmentation, enables us to extract the geometric shape, and, in turn, to only categorizeudas archaeological class those pixels belonging to geometrically (rectangular and linear) shaped clusters. Outputsudfrom this classification identify rectangular and linear features of archaeological interest whose size suggestedudthat they may be a farm and some sectors of an aqueduct, respectively. Results from satellite based analysisudwere successfully evaluated by georadar and geomagnetic prospection along with field survey. From georadarudand geomagnetic prospection we were able i) to confirm the presence of buried remains and ii) to detail andudcharacterize these archaeological features at the subsoil level as well as to define the local stratigraphy. Fromudfield surveywe dated the detected buried remains to a period spanning from Imperial Roman to early Byzantineudhistorical times.