tailieunhanh - Digital Terrain Modeling: Principles and Methodology - Chapter 3

Kỹ thuật để thu nhận các nguồn dữ liệu DTM Trong chương 2, các chiến lược lấy mẫu đã được thảo luận, về việc lựa chọn các điểm trên bề mặt địa hình (hoặc tái tạo âm thanh stereo mô hình). Trong chương này, các kỹ thuật được sử dụng để đo lường thực tế của các vị trí lựa chọn được trình bày. 3,1 Nguồn dữ liệu cho mô hình địa hình kỹ thuật số Nguồn dữ liệu có nghĩa là các vật liệu mà từ đó dữ liệu có thể được mua lại cho mô hình địa hình và nguồn dữ liệu. | CHAPTER 3 Techniques for Acquisition of DTM Source Data In Chapter 2 sampling strategies were discussed on the selection of points on the terrain or reconstructed stereo model surface. In this chapter the techniques used for actual measurement of such selected positions are presented. DATA SOURCES FOR DIGITAL TERRAIN MODELING Data sources means the materials from which data can be acquired for terrain modeling and DTM source data means data acquired from data sources of digital terrain modeling. Such data can be measured by different techniques 1. field surveying by using total station theodolite and GPS for direct measurement from terrain surfaces 2. photogrammetry by using stereo pairs of aerial or space images and photogrammetric instruments 3. cartographic digitization by using existing topographic maps and digitizers. The Terrain Surface as a Data Source The continents occupy about 150 million km2 accounting for of the Earth s surface. Relief varies from place to place ranging from a few meters in flat areas to a few thousand meters in mountainous areas. The highest peak of the Earth is about 8 884 m at Mt Everest. Most oceans are kilometers deep while some trenches in the Pacific plunge in excess of 10 000 m. In this book terrain means the continental part of the Earth s surface. The Earth s surface is covered by natural and cultural features apart from water. Vegetation snow ice and desert are the major natural features. Indeed in the polar regions and some high mountainous areas terrain surfaces are covered by ice and 31 2005 by CRC Press 32 DIGITAL TERRAIN MODELING PRINCIPLES AND METHODOLOGY snow all the time. Settlements and transportation networks are the major cultural features. For terrain surfaces with different types of coverage different measurement techniques may be used because some techniques may be less suitable for some areas. For example it is not easy to directly measure the terrain surface in highly mountainous areas. For this