A data structure for exchanging geographical information

Geographical information consists of non-spatial information (alphanumeric) and spatial information (vector and raster), the relationships between the non-spatial information and the spatial information, as well as the spatial relationships inherent in the spatial information, known as topology. It is undesirable for any exchange standard to lose, reduce or alter any information exchanged through the standard. For this reason, current alphanumeric and graphic exchange standards are insufficient for geographical information. The project team drawing up a proposed South African standard for the exchange of geographical information has studied the proposals and standards of other countries and has held discussions with the users and potential users of computerized geographical information in this country. The project team fells that the best model for use with the data structures of the exchange standard is the relational one. This paper describes the nature of geographical information and the advantages of the relational model