The Use of GIS for the Visual Exploration of Archaeological Spatio-Temporal Data

Article excerpt

Introduction

Treatment of the temporal component is a relatively new issue within the fields of cartography and geographic information systems (GIS). For archaeologists, however, straggling with time is traditionally a routine task and, although from a different point of view, this task appears to generate some areas of common interest between geo-information scientists and archaeologists. Areas of common interest--in a more general sense--can be found in literature (see, e.g., Peregrine 1988; Allen et al. 1990; Hinge 1991; Koussoulakou 1992; Lock and Stancic 1995).

The work described here is an attempt to combine the archaeologists' interest to keep track of time with GIS and cartographic representations and visualization of spatial, temporal and thematic aspects of archaeological excavations. The prototype system presented in this paper was tested at a prehistoric site in northern Greece. The large amount of finds at the site, their distribution in 3-D space, and the inspection of distributions in space and through time to determine attributes are all part of the archaeologist's work and formed the basis of the research described here. The goals are twofold:

* Interaction--through a graphical interface--with the database build on the basis of detailed paper forms and drawings of the archaeologists; and

* Generation of various views of the site and the finds, with options to select any combination of thematic and temporal attributes. This addresses the archaeologists' research interests in the characteristics, structure, and evolution of the site in space and through time.

The most typical element of the excavation is its extremely complex organization of layers dating back to various chronological periods. This is attributed to the long use of the site and its changing organization and structure through time. This fact occasionally makes interpretation of the finds difficult; often, architectural constructions of different periods are spatially close (horizontally and/or vertically), while elements of the same period can be located in different depths.

The research described here dates back to a cooperative project carried out by archaeologists and surveyors to develop fast, reliable, and efficient methods for recording and documenting the progress and the results of an archaeological excavation at a prehistoric site. Each excavation step was documented using photogrammetric methods, and the finds were stored in a database with the help of GIS tools. The data generated concern both architectural constructions and mobile elements, such as pottery and other objects. The data are plentiful and are expected to increase as the archaeological work progresses. Efficient and comprehensive methods are needed for data representation and visualization to enhance the work of the archaeologists.

The Excavation Site and the Finds

The excavation site is located within the city of Thessaloniki, in an area that is about three kilometers away from the coast and 80 meters above sea level. The site is on a hill occupying 18000 [m.sup.2] and rising 22 m high (Figure 1a). Because of its hill-shaped form, the site is known as "Toumbal."(1)

[Figure 1 ILLUSTRATION OMITTED]

The site was a settlement with various uses through time. The finds so far indicate that the area has been inhabited at least since the Late Bronze Age (i.e., starting from the 15th century BC.) and possibly even in the Middle Bronze Age (i.e., in the 15th to 20th century BC.). Excavation on the site has been going on for more than a decade, with about seven percent of the area having been investigated in various depths and at different locations (Kotsakis and Andreou 1989; Andreou et al. 1990; Andreou and Kotsakis 1991). The two main areas that have been excavated cover part of the top of Toumba and part of the hillside on its western side. These two separate spots were chosen for the purpose of correlating finds between them (Andreou and Kotsakis, 1994a). …