期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2000
卷号：XXXIII Part B4 (/1-3)
页码：670-677
出版社：Copernicus Publications
摘要：The geometry of spatial objects is generally determined through their boundaries. Photogrammetry, land surveying and digitising methods are based on this approach. This is however only possible if the objects are crisp so that their boundary can be identified. When objects are fuzzy this becomes problematic, or even impossible because their spatial extent is not fixed. For such objects uncertainty plays a role at three definition levels (Molenaar, 1998): - The existential uncertainty expresses how sure we are that an object represented in a database really exists. - The extensional uncertainty expresses that the area covered by an object can only be determined with limited certainty. - The geometric uncertainty refers to the precision with which the boundary of an object can be measured, if it can be determined. The geometric uncertainty plays a role in the representation of crisp objects, where the determination of the spatial extent is no problem. The extensional uncertainty plays a dominant role in the spatial representation of fuzzy objects, for these objects the geometric precision is not so relevant. In these cases it might even be doubtful whether the spatio- thematic data collected by a surveyor or obtained through image analysis gives sufficient evidence for the existence of an object, i.e. it might be that this existence is uncertain. There are many situations where the geometric and extensional uncertainty can hardly be distinguished. This paper will elaborate the concepts for describing object uncertainty at three levels and investigate how they are related. Crisp objects will be shown to be a special case of fuzzy objects
关键词：Spatial data models; uncertainty; fuzzy objects; geometry; vector data; raster data
