Deficiencies of sheets and tiles: building sheetless databases

A geographic information system (GIS) provides access to information for potentially large areas. Traditionally, cartographers have divided maps into sheets for technical reasons. While such units survive in digital databases, they serve a different function. The 'tile' system has limitations and deficiencies which must be understood by software developers and users. Remedies to the problems of tiles provide a basis for specifying the requirements for sheetlessness. A truly sheetless database depends on indexing algorithms, reviewed in a companion paper.