The direction relationship between spatial entities is an important content of spatial relations, and is the basis of more knowledge mining based on spatial data. In this paper, a vector spatial data direction relationship expression model based on azimuth is proposed. When the reference object and the source object are point spatial entities, line spatial entities and area spatial entities respectively, the direction relationship expression model is established. According to the need of natural cognitive language, the quantitative expression model and qualitative expression are transformed. We designed typical sample data, calculated each case in the model, and the results prove the feasibility of the model finally.
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