ORBIS is a multimodal network model of the Roman Empire, built by Walter Scheidel and Elijah Meeks, suitable for exploring historical transportation patterns based on traditional transportation network analysis. This paper begins with a brief description about how ORBIS was envisioned and ultimately came into existence, including a discussion about network analysis coupled with spatial analysis in spatial databases such as the PostGIS2 database where the ORBIS data resides. Of particular interest is the time-enabled and multimodal nature of the network, along with the variable edge cost based on duration, length or economic cost (what’s referred to in the parlance of the model as selecting either the cheapest, fastest or shortest routes). This allows the user to select different months and vehicles for travel, as well as other route-based restrictions, and their cost metric, to develop dynamic centrality measurements of the network based on time, vehicle and purpose of travel. The main thrust of this paper is on the use of ORBIS to identify historical phenomena using geographic network analysis. The core/periphery structure of the Roman Empire can be demonstrated using network analysis to identify dynamic distance from administrative centers. Other World Systems structures are visible, such as the variation between political/military, prestige good, information and bulk goods networks. The statistical identification of such structures will be compared to the visual representation of such structures using variable distance cartograms, developed for this project by Meeks in the network analysis toolkit Gephi as well as represented as a geographic network cost surface, where contours represent time (isochrone maps) or, as in the case of the attached figure, expense.
Finally, the suitability of geographic network analysis tools and methods for non-geospatial networks and the reverse will be touched on through the demonstration of distance cartograms used in genealogical and literary networks as well as an exploration of dynamic modularity within the ORBIS network over time.