Cartographic data structures: alternatives for geographic information systems

Means of capturing and encoding cartographic data for machine processing is a major issue in the design and the development of geographic information systems. The available and potential technology constitutes a bewildering array of choices for system designers from which to select formats and processing capabilities to meet user applications. Designers are not provided a very precise statement of data requirements (or fidelity requirements for the data capture and processing system); therefore, the tolerable distortion rates and tolerable information losses are not well expressed so as to assess coding efficiencies. Nor is there substantial agreement as to the appropriate breadth of comparative tests, as some systems can replicate coverages well for cartographic purposes, while other systems may provide stronger analytical capabilities for processing encoded geographic data.One of the major problems in encoding cartographic data is the lack of measures by which to assess the effectiveness of the coding. One set of effectiveness measures relates to the ability to replicate the source document in map form, while a second set of effectiveness measures relates to the use of the map or coverage data. There are a number of effectiveness measures that need developing in order to compare and test the effectiveness of alternative system approaches. A source document constructed to possess features that will test the effectiveness of alternative systems fairly and equitably needs development. This would result in the ability to establish benchmark tests by which systems could be compared.