1) The abstraction and visualization description: It should
achieved balance between the abstraction and visualization
description of 3D symbolic model. On one hand, visualized
materials should be summarized highly and drop the branches
down in order to express the basic characteristics. Usually, the
visual characteristics of objects should be retained or even be
exaggerated. These characteristics include appearance
similarity and material similarity, and so on. It should make
users think of features themselves immediately when they see
the symbols. Because the symbol is of high similarity, it can be
understood and accepted easily by users. On the other hand, it
should not blindly pursue similarity and simulation. Otherwise
it will make confusion about the difference between 3D
visualized model and simulation Landscape in 3D GIS.