How to get all boundry items from QgraphicsScene?

Hi,
I have drawn @200 GPS location points on QgraphicsScene/QgraphicsView
Now i want to draw a boundry line by connecting all points which are at boundry.
Is there any way of getting all points list which are at boundry from QGraphicsScene so that I can draw the boundry line?
Thanks in advance.

No, because there really is no standard way to define what is the boundary.
Qt only can give you the bounding rectangle of your points, but I guess that that is not enough for your purpose. You'll have to either find an existing algorithm to do what you want, or device your own. I think it is doable to find a simple polygon to surround all points, but I have never tried.
Anyway, you should probably look for "convex hull algorithms".
Edit:
Here is one "implementation":http://en.wikibooks.org/wiki/Algorithm_Implementation/Geometry/Convex_hull/Monotone_chain you might use. It is not the fastest algorithm, but probably fast enough for only 200 points.