What the vertical curve page covers
Omni's vertical curve calculator covers parabolic vertical curves, which are standard for transitioning between two roadway grades. The page defines BVC, EVC, PVI, elevation, gradient, and curve length before applying the equations.
Vertical curve equations
E_x = E_BVC + g_1 x x + ((g_2 - g_1) x x^2) / (2L)
E_PVI = E_BVC + g_1 x L / 2
E_EVC = E_BVC + g_1 x L + ((g_2 - g_1) x L) / 2
Symmetric-curve limitation
The fetched source explicitly notes that the page is for symmetric parabolic vertical curves. This version keeps the same scope and lets you evaluate the elevation at any horizontal distance x measured from the BVC.