Aerial Photography Meets Geophysics. Mapping the Hilltop Settlement of Montarice (Italy) by a Multi-Dimensional Analysis of Remote Sensing Imagery

Abstract

Excellent aerial imagery and geophysical data acquired over Montarice hill (Regione Marche, Italy) during the Potenza Valley Survey (PVS) project will form the subject of this talk. This promontory has a long settlement history, starting at least in the Middle Bronze Age but with significant centralised occupation between the 6th and 1st centuries BCE, between the later Iron Age and the Roman Republican period. Next to the overwhelming amount of pottery that has been collected during artefact surveys over the years, the site has also repeatedly revealed itself in terms of interesting vegetation and soil marks. This paper examines first the multi-dimensional potential of archived analogue and digital aerial archaeological photographs. Such an image dataset holds not only several inherent spectral dimensions which can be explored, but there are also three geometrical dimensions stored in the images. Comparing sequences of images over time even delivers an additional time component. The main idea now is to examine all the imagery taken since the start of the PVS project and explore the potential of state-of-the-art image-based modelling (IBM) techniques in reconstructing the three-dimensional geometry of the photographed hilltop site. Since dense image matching – as a part of IBM – allows to model the canopy of the vegetation at the moment of the photographic survey, it can yield a three-dimensional geometrical representation of the plants. The latter can be the focus of its own information extraction process, using techniques mainly developed in the fields of computer graphics and airborne laser scanning. However, the true power lies in the combination of the spectral and geometrical dimensions as this approach can even overcome hurdles that are typical for each information set on its own. In other words: the newly extracted geometry will be used to enhance the spectral dimensions of the imagery, hereby increasing the visibility and readability of the imaged vegetation (and soil) marks. In a second phase the interpretative mapping of the aerial data will be confronted with data from different geophysical operations on the site: full coverage magnetic survey and focused GPR and earth resistance prospections. The difficult integration of large amounts of remote sensing data and the interpretation of the complex interplay between ancient settlement dynamics and site erosion phenomena will be at the centre of the presentation.