ABSTRACT
Geographic information systems (GIS) need little introduction. Over the past twenty years, this technology has grown from rare to prevalent. Twenty, or even ten, years ago there were few operational systems. Recently, hundreds of systems have been sold to federal, state and local governments. Utilities, forestry, mineral and other industries are investing millions of dollars in geographically referenced data bases. One market study expects an investment of $90 billion in facility management systems before the turn of the century, while another study projects a solid start in this direction with $500 million in 1989. Despite these developments, the tools of analysis have not expanded at the same rate. A pervasive use of GIS technology simply automates traditional map overlays. In addition, most of the results do not include the likely error associated with the data.
