Correct answer: in the measurement, the north-south direction is defined as the longitudinal axis and marked as the X axis, and the X axis is positive in the north and negative in the south; Taking the east-west direction as the horizontal axis, marked as the Y axis, the Y axis is positive to the east and negative to the west. Quadrants I, II, III and IV of the measuring coordinate system are numbered clockwise. The definition of measurement coordinate system is different from that of mathematical coordinate system, and its purpose is to facilitate orientation, so it can be directly applied to measurement calculation without changing the mathematical formula.