Aerial survey
Aerial view of archaeological sites with :
1. Preserved structures 2. Relief traces 3. Crop marks 4. Soil marks.
Active aerial photography
It is a major aim of the PVS-project to supplement the static remote sensing material, e.g. existing vertical aerial photographs and satellite images (see further), by new images from the air with a more direct archaeological impact. This new material is thereafter integrated with information from other approaches, such as systematic field walking and intra-site geophysical work. Therefore, the program comprises a regular series of flights above the whole region to take aerial photographs from low altitude, with as major aims the detection, mapping, study and historical interpretation of the observed traces.
Our flying operations started in 2000, the exact year when aerial photography in Italy was liberalized from a formerly quite restrictive legislation. The flights are operated from several airbases in the area, such as the international airport of Ancona and a few smaller airbases in or near the Potenza plain. The aircraft most often used is a 180 horse power 4-seater from the Aeroclub of Ancona, manned with a local experienced pilot and one or sometimes two photographers. In general our survey method is traditional. Most flights are executed in spring, summer or early fall, although occasional winter flights were done. The observation altitude is about 1000 feet, while many oblique photographs are made at some 300-500 feet, using standard reflex cameras (24x36 mm) for slides with normal films and since 2004 digital cameras. The flying pattern consists of continuous crossings of the valley and surrounding hills under different angles and of intensive circling over chosen targets. A crucial part of the strategy is that once a potential site or important feature is spotted there is a regular follow up of that area during different seasons and in different weather conditions. Important also is the idea that rather small areas will be controlled several times a year, which makes it possible to organize a real follow up. We are convinced that this follow up of limited areas, such as the chosen transects for intensive fieldwork, is an important element in a full comprehension of the archaeological structures present in the soil. Indeed, one encounters many examples of truly remarkable 'evolutions' of archaeological sites due to totally different detection opportunities over different moments, seasons or years.
Three main approaches of reconnaissance over our study area must be distinguished.
In a first phase (2000-2001) the whole Potenza valley was photographed, with regular flights in different seasons. Many of the data obtained in this way support the geomorphologic and landscape studies in the area. Especially specific analyses, such as of erosion phenomena, the precise location of river terraces, ancient and modern water sources, fluvial movements through time and changes in land use, are much helped with the introduction of these detailed and flexible views from above. One of the typical geo-archaeological approaches much helped by such aerial photography is the movement of the river Potenza in the lower valley near its mouth, where a close relation with the fast changing archaeological landscape was observed. This was especially relevant for the location of roads, a river port, ancient land division, rural settlements, pottery production areas and bridges around the Roman colony of Potentia.
The second approach of active aerial photography (mostly between 2001-2005) aimed at the detection of previously unknown archaeological sites in the crops, ploughed fields and other surface coverage spread all over the valley. Here results are obtained by very regular flights in the whole Potenza region and especially in the three transects chosen for intensive field walking campaigns, respectively in the upper-, middle- and lower valley. In all areas, whether only extensively or also intensively field-walked, the potential archaeological indications from the air were checked on the ground. Special attention was also given to the areas of known archaeological sites in the valley, where no intensive remote sensing had been done before. This systematic aerial reconnaissance was followed up by systematic fieldwork, involving standardized registration, analysis, mapping and interpretation. All aerial photographs were stored in the Geographic Information System of the project. A GIS fundamentally links geometric data and non-spatial attribute data, allowing new ways of powerful data exploration, querying and analysis.
Since 2002 we also started a third approach to the archaeology of the region. Since then, intensive archaeological intra-site field survey work has been carried out on a series of large protohistoric (Picene) centres in the valley, as well as on the Roman towns situated in the Potenza corridor. From West to East these relatively small Roman cities are: Septempeda (San Severino Marche), Trea (Treia), Ricina (Villa Potenza) and Potentia (Porto Recanati). All of these sites – which are for most part totally abandoned since at least the early Middle Ages - have reasonable to excellent potential for non-destructive surface survey and because of the small scale of excavation work previous to our investigation of the area, much can be learned from an integrated survey approach. Our surveys are designed to improve general understanding of the topography of proto-urban and urban settlement in this part of Italy and to deepen our knowledge of the processes of early (mostly Roman) urbanisation in Le Marche. Within this site oriented approach the area of the selected large and complex sites was continuously monitored from the air, and especially intense flying during certain dry spring seasons (2003, 2009) has produced some remarkable images, locating and visualizing many aspects of the urban topography and of the suburban landscapes of the Roman valley cities and some of their protohistoric hilltop predecessors. Important efforts are being undertaken to enhance, rectify and map the most relevant archaeological features of such complex sites. To enhance the possibilities for detailed and precise mapping of buried features also tests were done with a so-called Helikite. To deal with cloudy conditions (or other particular situations in which the shutter speed becomes too long for conventional aerial photography) and allow us to obtain very detailed imagery of the large sites involved (in the visible, but also in the near-infrared and even ultraviolet range), a stable, easily maintainable and remotely controllable construction was created. It could be shown from the results obtained that this original instrument for Low Altitude Aerial Photography is capable of delivering imagery with a very small ground sampling distance, hence yielding so-called high spatial resolution imagery. Moreover, its low cost allows for a higher temporal resolution, as the platform can provide imagery from a certain archaeological interesting area at short intervals.
Aerial monitoring of the protohistoric site Montarice.
With the help of the software Airphoto 3.x a large number of crucial oblique photographs were rectified in order to map the archaeological features.
Technique of rectification of oblique aerial photographs .
After the desired images are rectified/restituted, they are used in ESRI‘s ArcView 3.2 GIS–software. Here, all the ortophotographs are displayed in their right geographical location. This enables a comparison of the features as well as the corrected raster images to serve as the basis for a vector layer which will hold the on–screen interpretation. To make the features become more distinct, some image processing might be advisable (the most common routines are also available in AirPhoto 3.x). The possibility GIS offers to add other digital information, as hydrological, geological and field survey data, can help to interpret the marks and increases the process‘ reliability. As the target map is on a scale of 1:10 000, this mapping method is adequate for the production of 1:10 000 (and smaller) archaeological maps.
Passive aerial photography
Besides storing our own oblique photographs, also existing remote sensing images are assembled and stored digitally. These concern, amongst others, satellite data and vertical aerial photographs for geomorphologic mapping and additional geo–archaeological detection and site–analysis. Different excellent series of vertical aerial photographs of the Potenza area, made by the I.G.M.I., R.A.F. and other institutes and firms, as well as some satellite data were studied in the GIS–environment. Comparing these different image sources, leads to a more complete archaeological and geomorphological image. Additionally, the dicrepancies between these distinct remote sensing products can produce new insights concerning the revealing of dissimilar feature types originating from different periods in relation to a particular remote sensing method.