[Lisp] How to filter list of point to get external contour

How to filter list of coordinates (2D) to get list of external contour.

I whant to make something simillar to attached image:

Maybe check Lee Mac's post HERE (Post #3).

IMO the concave sections in the desired contour are not logical.

You could start here and refine the boundary to suit your requirements.

IMO the concave sections in the desired contour are not logical.

True, better solution is to make contour without concave sections

You could start here and refine the boundary to suit your requirements.

Thank you Lee, that's it!