Objects with Fuzzy Spatial Extent

Abstmct The determination of the spatia) extent of geo-obiects is generally approached through their boundaries or, more precisely, thrcugh the positions of their boundary points. The analysis of the geometric uncertainty of the objects is therefore often based on accuracy models for the coordinates of these points. In many survey disciplines objects are mapped, however, that are not crisp wel) defined. In that case, the geometric uncertainty is not only a matter of coordinate accuracy, but also a problem of object definition and thematic vagueness. The spatial uncertainty of such objects cannot be handled by a geometric approach alone, such as the epsilon band method. This paper investigates the reasons for the fuzzy spatial extent of objects and proposes an approach to map the spatial extent of objects and their uncertainties when obiects are extracted ftom field observation dato. The relationship of uncertainties between thematic aspects and geometric aspects is investigated. A practical example of a coastal geomorphology study is discussed to illustrate the approach.