Abstract: The traditional method of map symbol filling on the “island” class patch will cause unreasonable symbol layout or symbol space conflict in sensitive areas, missing object attribute quantitative or sequential description. To this end, this paper proposes an “island” class patch symbol filling algorithm based on the constraint Delaunay triangulation. Firstly, regular meshing and irregular triangulation of discrete point groups corresponding to “islands” class patch, used to calculate equivalence points. Secondly, add “convex” and “concave” attachment points according to the additional criteria,connect equivalence points and additional points in sequence as the constraint boundary of Delaunay triangulation. Finally, construct a uniformly varying constrained Delaunay triangle network, integrate the primitives in the triangular network, and fill in the “island” class patch symbols. Experimental analysis using island boundary point data in electronic chart, compared with the traditional method, the “island” class patch symbol filled by this method is uniform various. Strong interactivity, easy for users to modify and switch, and perform secondary filling. The result shows that the method proposed in this paper is suitable for symbol filling of “island” class patchs.

Key words: “island” class patch, irregular triangle network method, constrained Delaunay triangulation, unit, map symbol filling