遥感教程第15-1页¶
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Applied remote sensing is (or can be) a key component in various types of decision making. As an example, consider how one goes about the process of converting now vacant natural landscape into an extensive living community: this includes housing developments and shopping and service centers plus sites for industry and transportation and utilities infrastructure. Much of the information needed is in the form of thematic maps (soils stability; topography; proximity to roads, etc.) and various data sets (land ownership; sources of water; local economy, etc.). Over the past two decades, a new systematic approach to gathering, storing, and manipulating the different information types, with the objective of analyzing the tasks and making and implementing decisions, has become highly popular and widespread in use: this is the methodology intrinsic to what is known as GIS or Geographic Information Systems. Remote sensing plays several roles - an obvious one is to upgrade certain maps that are outdated by classifying the most recent scene content into classes needed in any GIS analysis. This Section will explain in some detail the functions of a GIS analysis, will show how imagery like Landsat can be a vital part of the process, and will use two applications to illustrate the general end results sought. The first page focuses on some types of thematic maps in common use.
地理信息系统¶
地图和属性¶
在本教程中，我们展示了地球表面和云的照片和图像，其中一些还附带了定位、分类和描述物体的地图。所有这些物体都有一个共同的特征：它们是视觉上的、小型化的代表，或是地表上或地表上地理空间上的位置和特征类别的替代物，无论是陆地还是水。因此，它们描述了局部、区域或全球地理的各个方面，我们可以在X、Y（水平）和Z（垂直）图中以几何方式定位这些方面。我们可以参考这个图，然后，参考某种形式的坐标和投影系统。地图投影是使用经纬度网格网络，根据系统、有序的重新排列，将点或位置从球形球体转移到缩小的平面（地图）上的一种特殊方法。
照片（图像）和地图本质上是二维的或平面的，尽管我们可以使用轮廓或阴影等技术来呈现准三维的外观或提取广义基准面以上相对高度的信息。最常见的三维地图是地形图，我们已经在第11节中检查过了。 (page 11-1) ②正如我们在第10节和第11节中提到的，地图通常几乎总是具有以下基本信息：图形距离测量、比例、方向和方向、投影类型和一些地理坐标系，以及附带图例中的其他描述符和符号。地形图也有等高线间隔。
` <>`__15-1: What type(s) of map is/are the average citizen likely to encounter in everyday life? `ANSWER <Sect15_answers.html#15-1>`__
地图是照片和图像的人工衍生物，旨在记录各种各样的关于表面上特定特征类别的空间分布的信息。我们还将这些类别称为属性，它们是本质上非空间的一般描述符（它们取决于特征而不是位置）。一块土地，不管大小，很可能包含我们可以分配给不同类别的各种特征或特征；换句话说，它有许多属性。类别也可以是主题。例如，我们可能需要各种各样的主题地图来充分描述表面的内容。因此，假设面积为一平方公里（或一平方英里），一张这样的地图可以显示道路网络、另一个植被覆盖、第三个住宅或功能建筑、第四个适合挖掘的工程特性等等。我们可以在多用途地图上组合多个主题，例如道路、建筑物、休闲区等。一种常见的地图类型显示土地覆盖，它确定了我们可以在地图比例限制内显示的选定点或位置的适当类别。这张地图的一个变种是土地利用地图，其不同之处在于，它详细描述了人类活动所涉及或感兴趣的覆盖范围。
` <>`__15-2: Think of (and list) at least four other types of specialized thematic maps. `ANSWER <Sect15_answers.html#15-2>`__
|内华达州瓦肖县（里诺）部分土地覆盖类型地图示例：左侧=斜坡；中心=土壤；右侧=植被。γ
` <>`__15-3: Suppose you decided you wanted to live near Reno, but you are now residing in the eastern U.S. Your great Uncle has died and left you a piece of land. Explain how you could use the above 4 maps, even though "in absentia", to make an educated guess as to problems you might encounter in building a house, so you can start planning even before you get there. `ANSWER <Sect15_answers.html#15-3>`__
|休斯顿和德克萨斯州加尔维斯顿之间地区的综合地图，显示了1965-67年的平均月降雨量。|
` <>`__* 本节的部分内容已从陆地卫星教程工作手册的活动（第7章）中自由改编；该活动是由本教程的初始发起人、代码935的现任分支机构主管William J.Campbell先生于1981年编写的。
主要作者：Nicholas M.Short，高级电子邮件： nmshort@nationi.net