Direction refers to the position of the object relative to the reference point (the coordinate origin of the reference system). To determine the orientation of an object, we must first determine the reference point. For example, if a person is standing in the northwest corner of a sports ground, if the northwest corner is a reference point, this person's position is at the reference point, which can be expressed by (0,0); If the center of the sports ground is taken as the reference point, the due east direction is the positive direction of X, and the due north direction is the positive direction of Y, then the position of this person can be expressed as how many degrees west of North.