Figure 2.

(A) A case in which the current polyline does not have posterior connections and is, thus, a terminal fragment. In this case, the current fragment is added to the hierarchy. The green color shows polylines already added to the hierarchy which needs no further processing. (B) The current polyline has a posterior connection where the last point of the current polyline corresponds to the first point of the posterior connection. The two polylines are joined into a single polyline and this new polyline is processed (the blue color represents polylines to be processed). (C) The current polyline has a posterior connection at an intermediate point. In this case, the current polyline is split into two sub-polylines. The first sub-polyline is added to the hierarchy (green color). The second sub-polyline and the posterior connection are processed (blue color). (D) The current polyline has two posterior connections to its last point. The current polyline is added to the hierarchy (in green) and the two posterior connections will be processed (in blue).