Computer Applications of Archaeology

The Italian researches in Iranian Sistan started since 1967, under the Direction of Prof. M. Tosi and were carried out until 1978 when, cause the Islamic Revolution, all the foreigner équipes were obliged to let Iran.
During those twelve years the researchers collected a huge quantity of data, both from the survey and the excavation of the protohistoric site. Immediately it was clear that the landscape influenced in a very impressive way the settlement patterns of the Sistan area.
The Hilmand Delta in Sistan represents a clear case of instability evidently connected to the fact that the basin is sharply limited to the west by a N-S barrier made by the front of the Palang Mountains and their piedmont colluvial fans of gravel sediments. The first noticeable difference between the Hilmand and the other systems, such as the Murghab or the Nile, is the fact that the densest settlement areas and the capital centres have always been since the end of the 4th millennium BC at the end of the delta system, to connect the river as well as the huge terminal lake. The rapid built-up of sediments compels the waters to change their courses several times, while a circular anticlockwise sequence of descending lacustrine basins connected with each other by spillways, like the Sheelag rud, drains overflows to the southernmost sections of the basin. Satellite imagery of southern Sistan indicate some six or seven overlapping delta fans, all dated by the archaeological sites to later historical times, spanning over less than a thousand years in Islamic times. Even more unstable have been the southern limits of the Hamun, the largest and most perennial of the terminal lakes. What is left of this ancient sistems, mostly dating to protohistorical times, contemporary to Shahr-i Sokhta, is reduced to thin yardangs, columnar sedimentary residues shaped by the dominant winds. Third millennium BC soils, often black by the organic content, have been detected at the top of these yardangs about two meters above the present level. The combined action of the expanding lake and the wind erosion has lowered most of the ancient surfaces, destroying all residual evidence of the Bronze Age landscapes.
The Bronze Age mounds of Sistan, also strongly reduced in their size by aeolian action, rise on the takyr as isolated pillars, not unlike the yardangs around them. The fact is that lake and wind have destroyed most of the remains of Sistan, leaving us with few isolated archaeological sites, standing like pillars to represent the phantoms of the original settlements.
The first step of this work is to realise a prototype model able to give to the user a complete vision of the problematic of this region and to allow him to analyse through the computer the data of an excavation nowadays inappropriate to support a normal management.
The final aim is to use an archaeological landscape model to improve causes and effects, in a particular geomorphological and hydrographical situation, of the abandonment of the protohistorical site of Shahr-i Sokhta. Thanks to the GIS Based System for the study of the excavation of the "Burnt Building", the final user can check the hypothesis proposed until now but also give some new.
The satellite imagery of the area helped to improve other techniques of analysis, driving the methodology through the geoarchaeological interpretation of the digital data and maps. We used Landsat TM and Corona photos, overlapped with vectorial and alphanumerical data, to draw a model for the visualisation and a multidimensional analysis of the geomorphological evolution of the landscape and the settlement systems during the IV and the III millennium BC.
According to the available data, the methodology consists of the following steps :
- digitalisation of the site maps and ancient cartography on several layers, and their georeferecing on satellite images
- rectification of the satellite photos, and multispectral elaboration
- construction of a 3D model of the site of Shahr-i Sokhta
- texture mapping of the satellite photo on the model of the site of Shahr-i Sokhta
- check and analysis of the existing archives
- codification and integration of the different tables in a system for the management of databases (DBMS)
- digitalisation in CAD systems of the "Burnt Building" and Necropolis phase maps, keeping distinct every room or grave on a different layer and georeferencing of these maps
- queries for the realisation of phase, thematic and diachronic maps directly from the system
- visualisation of the 3D model of the site with excavation areas geo coded.

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figg. 1 e 2 Satellite Imagery Examples (Landsat TM and Corona).

fig. 3 - Dem and Vector/Satellite Imagery Overlays.

fig. 4 - 3D model of Shahr-i Sokhta Site and Exavation Squares Georefered.

fig. 5 - Thematic Maps relised by Gis System.