There are three differences between the rectangular coordinate system of the measuring plane and the rectangular coordinate system of the mathematical plane (Cartesian coordinate system): (1) The measuring coordinate system takes the north-south line passing through the origin, that is, the meridian, as the ordinate axis and takes it as the x axis; The east-west line passing through the origin is the abscissa axis and designated as the Y axis (the abscissa axis of the mathematical coordinate system is the X axis and the ordinate axis is the Y axis). (2) The rectangular coordinate system takes the positive direction of the X axis as the starting edge, and rotates the azimuth φ and I, II, III and IV quadrants clockwise (the mathematical coordinate system takes the positive direction of the X axis as the starting edge and rotates the inclination θ counterclockwise, which is divided into I, II, III and IV quadrants). (3) X) is mostly two big positive integers, such as Beijing local coordinate system origin coordinate y = 500,000m and x = 300,000m (mathematical coordinate origin coordinate x=0, y=0). Mathematically, the plane rectangular coordinates take the longitudinal axis as the Y axis, which is positive from the origin and negative from the origin; Taking the horizontal axis as the X axis, it is positive to the right and negative to the left from the origin; Quadrants are numbered counterclockwise. ? The plane rectangular coordinate system in the measurement takes the longitudinal axis in the north-south direction as the X axis, which is positive from the origin to the north and negative from the south; Taking the horizontal axis of the east-west direction as the Y axis, it is positive from the origin to the east and negative from the west; Quadrants are numbered clockwise.