Đang chuẩn bị liên kết để tải về tài liệu:
Digital Terrain Modeling: Principles and Methodology - Chapter 15 (end)

Ngoài mô hình hóa địa hình kỹ thuật số Chương 14 bàn về sự phát triển truyền thống và các ứng dụng của mô hình địa hình. Ở đây, chúng ta nhìn vào một số phần mở rộng của các mô hình này cho các vấn đề cụ thể. 15,1 MODELING địa hình kỹ thuật số VỚI XÂY DỰNG COMPLEX 15.1.1 Hướng dẫn Bổ sung Thi công xây dựng trên bề mặt địa hình Để đơn giản nó thường được giả định rằng các mô hình địa hình đơn điệu trong X và Y có chỉ là một Z có thể cho mỗi vị trí XY | CHAPTER 15 Beyond Digital Terrain Modeling Chapter 14 discusses the more traditional development and applications of terrain models. Here we look at some extensions of these models for specific problems. 15.1 DIGITAL TERRAIN MODELING WITH COMPLEX CONSTRUCTION 15.1.1 Manual Addition of Constructions on Terrain Surface For simplicity it is usually assumed that terrain models are monotonic in X and Y there is only one possible Z for each XY location. This is often true in the real world but not always occasionally there are caves tunnels overhanging cliffs bridges and overpasses. In the work by Tse and Gold 2002 the standard TIN model is extended by merging some aspects of terrain modeling TINs computational geometry the Quad-Edge data structure and computer aided design or CAD Euler operators which guarantee to preserve the connectivity of the surface after they are applied . They found it easy to combine them to give the usual operations on a 2D triangulation as well as add an operator that generates a hole between any two nonadjacent triangles which is really the same thing as adding a bridge or handle to the surface . Figure 15.1 Figure 15.2 and Figure 15.3 give simple examples and Figure 15.4 and Figure 15.5 show part of a Hong Kong city model. Thus a simple modification of the basic triangulation algorithm allows one to interactively modify the terrain model to add complex features that are otherwise unavailable. Because one is still forming a connected surface a variety of topological operations such as neighborhood selection and flow modeling may be performed. Clearly another even higher layer of operations would permit one to add predesigned features such as buildings dams tunnels etc. to our terrain model. 297 2005 by CRC Press 298 DIGITAL TERRAIN MODELING PRINCIPLES AND METHODOLOGY Figure 15.1 TIN model of a surface with a tunnel a a tunnel on a TIN model and b the enlarged tunnel. Figure 15.2 TIN model of a surface with bridges a two bridges on a TIN model