INTEGRATED TECHNOLOGIES FOR THE MAPPING AND THE MANAGEMENT OF THE TUSCAN ARCHAEOLOGICAL HERITAGE
The Geographical Information Systems - as well-known - represent the best solution actually available for the management,
the analysis and the integrated interpretation of spatial data. On this basis, in 1993, the Chair of Medieval Archaeology of the
University of Siena (Prof.Riccardo Francovich) started experimenting GIS platforms applied to the management of the large amount
of landscape data collected in the past years. The Archaeological Map of the Siena Province was designated as a pilot-project todevelop
an archaeological GIS; in 1995 the Atlas of Tuscan Fortified Sites project followed and since 1999 we activated projectsaimed at a digital
recording of all published archaeological evidence and of religious buildings within regional boundaries.Process of archaeological
cartography have been based on different methodologies of investigation. Within the Department ofMedieval Archaeology, the Laboratory
of Aerial Photographic Interpretation has been active since 1984. The Laboratory isdedicated to the stereoscopic examination of historical
vertical aerial photographs and in twenty years it has carried out numerous research projects, leading to the identification of over 5000
air-photo anomalies in Tuscany and 500 in Umbria.
The need to increase the archaeological record, the changing in Italian law on aerial photography, the development of remote sensing
techniques and of the software for the processing of imagery addressed the interest of the area of Medieval Archaeology to the application
of innovative remote sensing techniques with particular attention to:
- The analysis of panchromatic and multispetral satellite imagery. In the spring of 2000 and 2002 we acquire 470 sq. km of Ikonos-2 data
(geometric resolution 4 m) and 200 sq. km of QuicBird-2 data (geometric resolution 2,7 m for the multispectral and 0,70 m for the
panchromatic). The procedure followed in processing the Ikonos-2 imagery falls into two main phases. The first consists of a series of
standard transformations of the whole image. In this stage of the processing some of the most commonly used techniques have been
contrast stretching, density slicing, RGB colour composites of the original bands (3-2-1; 4-3-2; 4-2-1; 3-4-1), arithmetic manipulation,
in particular averaging (to reduce the noise component) and rationing (NDVI), Principal Component Analysis, Tasseled Cap Transformation,
Decorrelation Stretch e colour composites RGB of results of various transformation (in particular PC1-PC2-PC3; BGW). This phase plays a
central role in the identification of archaeological features. In the second step we use the GIS system to make comparisons with the features
identified in the various GIS layers. This step has been useful in preventing other kinds of misidentification, for instance of
non-archaeological features. In the case of QuickBird-2 data the availability of panchromatic layer allow us to operate a data fusion
between panchromatic and multispetral data (algorithm pan sharpen) to obtain a new data with three band (near-infra red; red; green)
with a geometric resolution of 0,70 m.
- Aerial survey and oblique photography. The opportunity to develop a programme of oblique air-photography for
landscape investigation first presented itself in 1999 during the University of Sienas XIth International School in Archaeology.
In anticipation of imminent changes in Italian law on aerial photography, the possibility of organizing an air survey program was
discussed with English Heritage. In the spring of 2000 we carried out preliminary aerial reconnaissance to check at first hand the
potential and limitations of oblique air-photography in the landscape of Tuscany. Then, at the end of May 2001, twenty-one post-graduate
students engaged in the areas of research and heritage conservation took part in the first Aerial Archaeology Research School to be held in
Italy. In the following years the research program has been carried out systematically and actually at the Department of Archaeology and
History of Arts of University of Siena is available an archive of 8500 oblique aerial photographs.
Ground-truthing and geophysical survey. In the spring of 2001 we started, in collaboration with the Department of Earth Sciences
(Chair of Geophysics prof. Dario Albarello), to test the magnetic method during the ground-truthing of the features identified during
the analysis of aerial photographs and satellite imagery. The good results has convinced us of the great potential of this method and
we decided to buy a Overhauser gradiometer. In a field survey carried out in Val dOrcia (Siena administration) during the months of
August and October 2003 we progressively tested a system of acquisition that allowed us to cover one hectare per day at a resolution
50 cm along traverses which were each set 1 metre apart. So far we have acquired 10 hectares of magnetic data.
- Digital photogrammetric techniques. The photogrammetry represent the last technique we introduced in our landscapes
projects. This technology allow to produce very accurate maps of the landscapes (for instance very detailed micro digital terrain model)
and archaeological features.
Actually, in total, the archives of satellite, aerial and magnetic data are stored in the cartographic server (about 100 GB of data).
The main software we adopted to integrate all the remotely sensed data we collected and the technical, thematic and historical
cartography is ArcGIS (ArcView and ArcInfo) produced by ESRI. The choice is related to the widespread diffusion of this suite.
In fact the ESRI package represent the commercial standard adopted by most public administrations that are our major cartographical
suppliers. Collaborations and agreements with public administrations has allowed us to acquire, in the last four years, more than 60
Gigabytes of cartographical datasets in different formats and reference systems (Gauss-Boaga representing the Italian standard and UTM
representing the world standard).
The remotely sensed data and the cartographic data are managed within a client-server architecture, with different access privileges in
order to permit visualization to everybody and modifying of information only to authorised users.
A crucial step in the process of archaeological cartography using remotely sensed data is represented by the interpretation of the
information in the GIS environment. The result of the observation, reading and interpretation of an images acquired by every kind of
sensor from satellite, to photogrammetric camera, to common reflex camera or to geophysical instrument is represented by the features
we are able to draw on a GIS layer and that we consider to be archaeological information. The work of storing on our GIS platforms the
exact perimeter of archaeological evidence gives us the real shape and dimensions of a site, enhancing the traditional cartographical
concept of point-shaped symbology. In conclusion, the project we propose could end up in developing a mature experience, which has
acquired and built up in time all the necessary tools, knowledge and skills in order to put forth an efficient and innovative management
of archaeological heritage.
