Discrete objects and continuous fields are fundamental conceptualizations of space and the basis for models of process. Spatial objects are the things that occupy the geographic world, described and measured in various ways as points, lines, areas, or volumes. The discrete-objects perspective is a traditional way of characterizing spatial patterns and is embedded in the uses of geospatial tools such as cartographic mapping and GIS. Powerful insights into spatial processes often require a re-conceptualization of phenomena from objects to fields. Conceptualizing the geographic world as a series of continuous surfaces (fields), each mapping location to the value of some variable, permits representations of gradient, slope, and aspect, and allows for volumetric, visibility, and least-cost-path analyses.