For acquiring the hierarchical spatial knowledge to be applied in cognitive route directions

a method of extracting hierarchical landmarks from urban POI data according to their significances is proposed.After analyzing the factors influencing the significances of POI objects from public cognition

spatial distribution and individual characteristics

a significance measure model composed of three vectors which are public cognition degree

urban centrality degree and characteristic attribute value is constructed.Then

the processes of computing the vector values of POI objects are discussed by the methods of questionnaire survey

multi-density spatial clustering and data normalization respectively.An experiment is carried out to compute the significances of the POIs selected from the area of Wuchang region of Wuhan city

and the POIs with different significances are treated as landmarks in different levels at last.In this experiment

several levels of landmarks are extracted

and being used as seeds to compute weighted Voronoi diagrams in every level

to reflect the influence area of every landmark and associate the landmarks in the same level and between the sequential levels.