Providing spatial statistical data analysis functionality for the GIS user: the SAGE project

Geographical Information Systems (GIS) are being used in a growing number of application areas. As a consequence there have been frequent calls to expand the range of spatial analysis tools available to users of GIS but a reluctance on the part of GIS software vendors to include such tools in standard software packages. An alternative approach is to link extra tools to GIS packages which raises a series of issues, such as, What sort of tools should be included? How should the linkage be done? To what extent can the functionality of the GIS be used? This paper draws on the results of a project in which software for statistical spatial data analysis (SSDA) was linked to ARC/INFO to produce a software system called SAGE. The statistical tools implemented included those which were felt to be useful to the general GIS user (as opposed to the specialist spatial statistician or econometrician), and they were linked to ARC/INFO using a client server architecture. The GIS was used within the context of SSDA for map drawing, spatial queries and operations on the topology of the spatial data, although it was found that the map drawing facilities of ARC/INFO were not well suited to the needs of this application. One of the conclusions of the project was that many of the techniques of exploratory spatial data analysis, such as providing graphical data summaries and linking these to cartographic views of the data could be easily integrated into existing GIS packages, providing a useful addition to their functionality for many GIS users. Many of the other SSDA facilities are probably still best provided in specialist software, but there is a need for a robust and standardised means for such software to extract information about the topology of spatial data from within GIS packages.