In place of a line bent every ten metres to keep within 0.1 m of every bump,
the grades and the vertical curves are fitted to the ground the way the
profile fits them. Where the formation is made in the terrain model the line
keeps to the radius of the norms and cuts and fills; over the ground left as
it is it bends as sharply as it has to. The joints keep the height and the
grade of the track joined, no grade is capped and no piece is under 5 m.