To look after a medieval estate, one required a map, an indexed account book and an abacus (Figure 1). For its time, this was a highly sophisticated geographical information system. Looking after the Earth and each of its parts requires more data, a better index and more data processing. Computer-based geographical information systems (GIS) can assist with these tasks. Unfortunately, the title "GIS' is user-friendly only to the initiated. For them, it is short, comprehensive and convenient. Each word reminds them of a significant point:
For the non-expert, "GIS' is a vacant piece of jargon. Published definitions run along the following lines:
A powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes. (Burroughs, 1986)
A system for capturing, storing, checking, analysing and displaying data which are spatially referenced to the earth. (Maguire, 1991).
These definitions emphasize the potential uses of GIS in geography. They do not refer to planning or design, and they are not very helpful in explaining the superiority of a computer GIS to its medieval precursors. Readers with experience in the use of computer programs for graphics, database and spreadsheet work can think of the GIS as a union between these three programs: spatial data replaces the medieval map, a database program replaces the indexed account book, and a spreadsheet program replaces the abacus. As spreadsheet and database programs overlap, a GIS could be described, simply, as a "spatial database'. Is the computer essential? No. But it saves time, improves accuracy and enables a more comprehensive viewConsider the example of an address list that has been taken into a cell-based spreadsheet (Figure 2). Field B is a column of names, Field C contains their street addresses. Other fields could hold other tabular data (for example, on family sizes, planning applications or whatever). To make this data "spatial', or "geographical', extra fields are required. Fields D and E contain x- and y-coordinates that define the geographical location of each address point. Field F could have z-coordinates, giving height data. The arrows indicate how data of this type can be used to generate maps. This is a GIS. It is not a magic technology: it is a spatial database. But a GIS does have the capacity to make planning more creative, more useful, more popular and more fun.
6.1A medieval GIS: book, map and abacus
Fig 6.1 A medieval GIS, comprised an account book, an abacus and a map