*On 06/08/2017 at 14:51, ***xxxxxxxx** wrote:

What kind of center do you want, and what for? An ngon is not necessarily planar, not necessarily convex, and not necessarily non-self-intersecting. The "center" may not even lie on the surface of an ngon even for a planar one. So what you are looking for depends on the purpose.

Easiest mean may be (max-min)/2 for each coordinate and all points (but this will put more emphasis on outlying points). You already mention the mean of polygon centers, or you could use the mean of points (which will put emphasis on dense subpoly areas). Or you could go for the centroid as the article describes.