Research On Creating Buffer For Space Object In GIS

Based on the present research on buffer analysis, this paper mainly studies the algorithm of buffer zones generation for space objects. These studies are based on the advanced theories and technical achievements of some interdiscipline such as 3D computer graphics, computational geometry, Geographical Information System (GIS) and OpenGL.With existing algorithms of buffer zone generation assessed, the paper proposes a new algorithm of automatic buffer zone creation based on method of circular arc for convex vertex and topologic space relationships of objects. The algorithm solves the problem of unequal width caused by method of angular bisectrix and avoids the distortion problem caused by method of circular arc for convex vertex. It not only can generate buffer zones for point, line, plane surface and compound objects, but also can generate buffer zones for the special objects with self-intersecting and containing several holes. In the process of merging overlap buffer zones for compound objects, an efficient vector algorithm of getting the intersection set and union set of two complex polygons is proposed, which is based on computational geometry and set theory. At the same time, an improved filling algorithm of scanning line is put forward in the paper, based on such idea as from down to up, from left to right. The method can fill any graph, including the complicated boundary graph with several holes.A algorithm of 3D buffer zones generation for space objects is presented in the paper. The algorithm is based on the topologic space relationships of objects, the special points on buffer zone and subdivision method of triangular facets and rectangular facets to generate 3D buffer. The processes of 3D buffer creation for point, line, face and convex polyhedron are introduced in detail in the paper. At last, the paper introduces dynamical exploring and realistic image drawing technology of 3D buffer using OpenGL.