This command converts a 2D polyline into a 3D polyline using a
slope from a reference 3D polyline or point. For example, this
command can be used to elevate a bottom-of-bank polyline given an
elevated top-of-bank polyline and bank slope. After selecting the
polyline to elevate and the 3D reference, there is a prompt for the
slope percent. Use negative for downhill. For each vertex on the 2D
polyline, the program finds the nearest position on the 3D
reference and assigns the vertex elevation using this reference
position elevation plus the slope multiplied by the distance from
the vertex to the reference.