chapter  2
21 Pages

Geographical information concepts and spatial models

This chapter provides an introduction to the principle of data storage in computer files and databases. At the level of a computer's storage facilities, it is shown that how spatial objects and their attributes can be allocated to logical units of storage such as fields, records and files. These in turn are represented by physical units of storage, such as bytes, words and blocks. The organisation of the computer's data storage can be made to reflect the logical structure of the spatial models such as the sequence of points in a line or the membership of a feature classification. This may be done by controlling the order in which fields and records are stored, or by linking associated records and files explicitly by means of pointers, in linked lists, or logically by means of unique key fields. The chapter addresses the subject of raster data storage and some of the commonly used techniques for compressing raster and image data.