The ground profile is derived directly from the terrain which has been  previously inserted to the program. The polyline which defines the road profile, can manipulated visually on screen (insert, delete, move operations on each VPI). After the insertion, the user is able to modify easily the geometrical properties (Ch., Hr, R) of the vertices that define the profile grade line.

One of the principle operations of DIOLKOS is the terrain reading. The program at design time, queries the linked terrain database. This database is stored in the form of Triangulated Irregular Network. Alternative the ground reading can be done from a batch of 3d lines describing the terrain (e.g. contour lines). In some design cases this way is preferable.

Help points are used frequently during the design of vertical alignment. These points are derived from the cross sections planes and placed to the corresponding positions of the vertical alignment.

When the user modifies the polyline vertices which defines the road profile the values of grades and ground elevation difference for all stations are updated on the screen at the same time.