Representation and Manipulation of Spatial Data

Abstract

In this chapter we present a number of methods for spatial data representation and manipulation. In kee** with the classification scheme of application domains into field and object-based applications, we divide these methods into field and object-based representation and manipulation methods. In field-based representation, the geographic space is partitioned (tessellated) into cells that are disjoint and that collectively cover the entire geographic region under study. Geographic objects are embedded in the space, and are described as well as manipulated in terms of the individual cells. For example, in this representation scheme, a lake would be described by the cells that cover its interior, rather than the polyline constituting its boundary. In this sense, the tessellation model is area oriented where the emphasis is on the content of the area rather than its boundary. Tessellation models can be further subdivided into fixed and variable spatial resolution models [Laurini and Thompson, 1992]. Fixed spatial resolution models use a geographic data structure called a raster, which consists of polygonal units of equal size. These units are used to describe geographical features. Variable spatial resolution models use units of variable sizes at a given level of resolution.