tailieunhanh - Digital Terrain Modeling: Principles and Methodology - Chapter 4

Mô hình hóa bề mặt địa hình kỹ thuật số Trong chương trước, kỹ thuật cho việc mua lại các nguồn dữ liệu DTM đã được thảo luận. Ngoài ra, mô hình hóa bề mặt có thể được áp dụng cho việc tái thiết của bề mặt địa hình. Đây là chủ đề của chương này. KHÁI NIỆM CƠ BẢN CỦA MODELING MẶT Nội suy và mô hình hóa bề mặt Một mô hình địa hình kỹ thuật số là một mô hình toán học (hoặc kỹ thuật số) của bề mặt địa hình. Nó sử dụng một hoặc nhiều chức năng toán. | CHAPTER 4 Digital Terrain Surface Modeling In the previous chapter techniques for the acquisition of DTM source data were discussed. Also surface modeling could be applied for the reconstruction of terrain surface. This is the topic of this chapter. BASIC CONCEPTS OF SURFACE MODELING Interpolation and Surface Modeling A digital terrain model is a mathematical or digital model of the terrain surface. It employs one or more mathematical functions to represent the surface according to some specific methods based on the set of measured data points. These mathematical functions are usually referred to as interpolation functions. The process by which the representation of the terrain surface is achieved is referred to as surface reconstruction or surface modeling and the actual reconstructed surface is often referred to as the DTM surface. Therefore terrain surface reconstruction can also be considered as DTM surface construction or DTM surface generation. After this reconstruction height information for any point on the model can be extracted from the DTM surface. The concept of interpolation in DTM is a little different from that of surface reconstruction. The former includes the whole process of estimating the elevation values of new points which may in turn be used for surface reconstruction while the latter emphasizes the process of actually reconstructing the surface which may not involve interpolation. To clarify this matter further surface reconstruction only covers those topics concerned with how the surface is reconstructed and what kind of surface will be constructed. For example should it be a continuous curved surface or should it consist of a linked series of planar facets In contrast interpolation has a much wider scope. It may include surface reconstruction and the extraction of height information from the reconstructed surface it may also include the formation of contours either from randomly located points or 65 2005 by CRC Press 66 DIGITAL .