Positioning apparatus and a positioning interval control method

A portable terminal includes a body movement sensor configured to detect a movement of a user; a normal moving pattern storage unit configured to store, in advance, a normal moving pattern; a moving state determination unit configured to determine the moving state from the movement; a normal moving certainty calculation unit configured to calculate a normal moving certainty indicating a degree of coincidence between the normal moving pattern and the moving state determined at time of detecting the movement; a position measurement interval controller configured to calculate a position measurement interval depending on the normal moving certainty; and a positioning unit configured to measure a current position of the portable terminal at the position measurement interval.