Over the last decade or so, developments in information technology (IT) have had a major impact upon the manner In which spatial data can be handled. Two separate developments have been in progress. One of these, digital mapping, allowed existing maps drawn on paper to be converted Into digital form; as a result, graphic data could be processed and displayed in different ways. The other, the development of sophisticated database management systems, has allowed large volumes of textual data to be stored, retrieved and processed. The two developments have now been linked into what are variously called geographical or land information systems.