That very much depends on the allowed shapes of that contour. If it's
known to be convex, it's trivial. If not, it's an ill-defined
problem, because there are quite a lot of polygons you can build from
a given cloud of vertices, and you don't provide any hint which of
them might be the right one.
Your best bet is to re-investigate where those points came from: do
you really have *no* idea which pairs of those are neighbours along
the contour line?
Hans-Bernhard Broeker ( XXXX@XXXXX.COM )
Even if all the snow were burnt, ashes would remain.