The calculation of subgrade elevation is based on the data on the longitudinal section diagram given by the design. Some designs will give the elevation of each structural layer, while others only give the final pavement elevation, and then the construction surveyors will calculate it by themselves according to the design requirements. The elevation usually given is the central elevation of the road, and then the slope of the cross section of the road should be considered when calculating the elevation of the side piles of the road.
The coordinates of middle pile and side pile shall be calculated according to the control coordinates given in the design. Some designs will directly give the coordinates of some points on the road centerline, and then determine the position of the whole road according to these points. Some will give the coordinates of several control points and then tell you the relationship between these control points and the road, so as to determine the location of the road.
A more convenient but stupid way is to draw the road center line and side line with the ratio of 1: 1 on cad, and then find points on these lines. Every time the cursor captures a point, cad provides a coordinate, and the error of cad is about a few millimeters. The only thing to note is that the designed geodetic coordinate system is opposite to the Cartesian coordinate system used in cad, that is, the X-axis data and Y-axis data should be exchanged. Then directly above or due north. There is usually a very simple rule in a straight line segment. Every 20 meters, every two adjacent piles have the same change in coordinate data. Simple addition and subtraction, curve segment needs special calculation, circular curve is slightly better, transition curve should be careful, and piles should be denser.