Imagine standing in a ditch and being able to see the shape of the ground along a line. Basically that is what a profile is, a travsverse plot of elevation with horizontal distance along a centerline across the earh's surface.

Knowledge of a skyline road's profile is crucial to determining what the deflection and payload capability will be for a particular yarder setup. Can you see below why a concave slope profile(bottom) is better than a convex profile?