（2）Terrain data is commonly regarded as the most important basis for most of geo-analysis. However, the automatic depiction of earth’s relief is one of the most difficult tasks in GIS. The earth’s surface is an irregular three-dimensional continuum, then it is impossible to be fully defined and fully depicted with an infinite number of points only. DEMs are a means of terrain representation in which elevation is recorded at specific horizontal positions. Burrough (1986) defines DEM as “Any digital representation of continuous variation of relief over space”. The methods are needed to capture and store elevation data over intermediate or large areas. DEMs can be grouped into the following basic approaches: regular grids (raster), triangulated irregular networks (TIN) and contours. Each has its advantages and limitations in different applications, but raster based on DEMs has got more popularity in applications.

汉译英

二十世纪以来，人们对地形图和地表的专题地图的需要量迅速增加。但由于纸制地图在收集、编码和重新利用地图包含的信息时产生了不良的后果：（1）原始数据量必须大大压缩或分类，才能使地图易于理解和表示，因而综合、损失掉许多碎部特征；（2）地图描绘必须极为精确；（3）信息的绝对容量意味着：比例尺一定时，一个大面积制图区域需要用多幅地图描绘；（4）一旦数据表示成地图后，要从中恢复某些数据以便与其它空间数据组合分析时显得很困难且费用高；（5）印刷地图是静态资料。由于以上原因，地理信息系统技术的出现为制图学带来了新的革命。

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GIS考研试题

一、（20分）1.地理信息科学2.数字地球3.数字地形模型 4. WebGIS 5.开放式的GIS

二、试述地理信息系统的设计方法并进行对比分析。（20分）

三、试述地理信息系统空间分析功能及其相应的应用。（20分）

四、试述GIS的集成模式。（20分）

五、简述地理信息系统的热点问题及今后的发展趋势。（20分）