Was surprised when I just created a ruled surface between 2 contour lines. There are very significant variations between the edges of the created surface (blue in the image below) and the contours (white) ... I would have expected the surface to follow the contours much more closely (the only places they seem to coincide are at the contour nodes).
RuledSurf.png (13.7 KiB) Viewed 4400 times
David Henderson