A. Surveying is to find the elevation of points having the same contour interval
B. Surveying is used to find the elevations of given points with respect to given or assumed datum
C. Surveying shows the relative positions of the objects on the surface of the earth
D. All of the mentioned
Explanation: Surveying is defined as determining the relative positions of points above or beneath the surface of the earth by means of direct or indirect measurements of distance and direction and elevation.