This paper presents a novel tangent based path planning method. The planner makes use of the obstacle contours to model the environment in a discrete 2D configuration space. Locally shortest paths are constructed by convex hulls and tangents. Complex terrain is effectively decomposed by the Trunk Structure. It makes a major improvement over the tangent graph approach by expanding only necessary parts of the tangent graph and using the Bouncing Scan technique. It is capable of large space, can take full advantage of sparse environments and deal with unknown and dynamic environments, which make it an ideal planner for long range navigation. Simulation results show that it generates global optimal path in most situations, and is very time and space efficient thus suitable for real time applications.