Hi Pilou, I don't believe that your method generated proper results...

For example this curve is the highest one, and I think the way these topo lines work, that is supposed to be a plateau there:



However, your version appears to have made it a ridge that drops off quickly to the bottom level, rather than a plateau.

I don't know if you need to adjust the curves by closing each of them, or if the tool you are using is not the right tool for this kind of situation... Or maybe I don't understand what the proper result is supposed to be..

- Michael