@Mark Why a comment and not an answer ? Anyways "then if you are outside you will come to a point on the convex hull from which you can see that the whole fence is on one side of you and there is no fence on the other side" - at that point, looking at any other angle, you'd see the sea which is simpler right ? This is the algorithm I originally thought about - walk the fence and look at all angles for the sea. Obviously this would work, but the "1 meter" solution seems faster if you don't have line of sight and have to walk every time

And it seems W_i is the quermassintegrale (appearing in Kubota's formula)... Well I don't really have to understand it all they way but I'm just wondering, how did you come up with 6.28 if you didn't have the formula in front of you ?

Well i think n is the same one from E_n which is the convex set, does that help ?

Just a quick question - What are n and W_i in the formula ?

Thanks ! Any chance for a link I can read without getting the book ?