An isoline rendering method considering of constrained conditions

An isoline map rendering method considering constrained factors is introduced in this paper. When constructing TIN, the constrained points are also inserted into TIN. It divides constrained factors into two types according to the geometry type, which are polyline and polygon. The method of embedding polyline an polygon constrained factors into TIN is brought out. When tracing isolines, it first calculate the intersection of line segments between a specified equivalent surface and the triangles in TIN, then connect these intersection line segments to form a complete isoline. It uses an binary tree to store the isoclines´ topological relationship so as to fill the isoline map conveniently. Finally, an example is given out to prove the method´s practicability.