Spatial relations are extensively used in spatial database query language

content-based spatial data retrieval and spatial data analysis. The uncertainty is an inherent characteristic of spatial relations

but little attention was paid to it. In this article

firstly

the definition

the implication of uncertainty of spatial relations and their influences on application of spatial relations are presented. Secondly

the sources of uncertainty spatial relations from the uncertainty of spatial data

spatial recognition and processing of spatial relation are analyzed

and the framework of processing uncertainty is proposed. Thirdly

the qualitative methods of describing spatial relations are evaluated and their shortcomings are pointed out. Finally

the fuzzy set theory is introduced to describing the fuzziness of spatial relations. The fuzzy methods can describe the partly membership between a geometry spatial relation and a concept. The fuzziness of spatial objects

people's cognition to spatial relations and similarity between two spatial relations can be described in a unified method

and spatial relations between two crisp objects

between two fuzzy objects and between crisp objects and fuzzy objects can also be expressed in a unified method. The fuzzy method lays a foundation for researching uncertain spatial relations.