Z 
Z 
P2-5-6 
(a) Conventional 3D coordinate system with (b) Proposed 3D coordinate system with 
vertical z-axis and oblique xy-axes oblique z-axis and orthogonal xy axes 
Fig. 1 Proposed 3d coordinate system for 3d view map 
(b) Number of Polygon Shift 
Fig.2 Concept of polygon shift method 
(a) A simple case with convex shaped buildings 
(Closer building hides a part of farther building) 
Fig. 3 Hiding and hidden buildings 
(b) A complicate case with a concave 
shaped building (it is difficult to judge 
which building is closer or farther).