Editing Quadtree (section)

====Node structure for a point quadtree====
A node of a point quadtree is similar to a node of a [[binary tree]], with the major difference being that it has four pointers (one for each quadrant) instead of two ("left" and "right") as in an ordinary binary tree. Also a key is usually decomposed into two parts, referring to x and y coordinates. Therefore, a node contains the following information:
* four pointers: quad[‘NW’], quad[‘NE’], quad[‘SW’], and quad[‘SE’]
* point; which in turn contains:
** key; usually expressed as x, y coordinates
** value; for example a name