Cardinal direction relations are binary spatial relations determined under an extrinsically-defined direction system (e.g., north of). We already have point-based and region-based cardinal direction calculi, but for the relations between other combinations of objects we have only a model. We are, therefore, developing heterogeneous cardinal direction calculus, which allows reasoning on cardinal direction relations without regard to object types. In this initial report, we reformulate the definition of cardinal direction relations, identify the sets of relations between various pairs of objects, and develop the methods for deriving upper approximation of converse and composition.
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