说明：  一本关于DEM的书籍。很强大，充分概括了DEM的基础知识、数据获取、表面建模、数学模型、数据组织、地形分析等等问题。
(A book on DEM. Very powerful, fully outlines the basics of the DEM, data acquisition, surface modeling, mathematical modeling, data organization, terrain analysis and so on.)