Conceptualizing the geographic world as a series of continuous surfaces, each mapping location to the value of some variable, permits representations of gradient, slope, aspect, and allows for volumetric analysis, visibility analysis, and least-cost paths. In '. . . the continuous-field view, reality is a collection of continuous surfaces, each representing the variation of one property over the Earth's surface. When it is necessary to differentiate by height, the field becomes three-dimensional rather than two-dimensional, and time may add a fourth dimension. Mathematically, a field is a continuous function mapping every location to the value of some property of interest.' For more information, see
http://www.spatialanalysisonline.com/output/
