28遥感的基础.docVIP

Unit 28 Fundamentals of Remote Sensing （遥感的基础） What Is Remote Sensing? For the purposes of understanding the concepts of remote sensing, the following definition should be given first: [CCRS, 2003] “Remote sensing is the science ( and to some extent, art) of acquiring information about the Earth’s surface without actually being in contact with it . This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.” 为了了解遥感的概念,给出下面的定义: （加拿大遥感中心，2003） “遥感是在不直接接触的情况下，获取地球表面信息的一门科学（某种程度上可以称之为艺术）。这是通过感知、记录和处理、分析,并应用反射或者发出的能量信息实现的。” In much of remote sensing, the process involves an interaction between incident radiation and the targets of interest. This is exemplified by the use of imaging systems where the following seven elements are involved. Note, however that remote sensing also involves the sensing of emitted energy and the use of non-imaging sensors (Figure 1). 在绝大多数的遥感中,该过程包括入射辐射和感兴趣区域的互动。这个可以在使用了如下七个要素参与的成像系统中得到例证。注意,遥感也包括了辐射能量的感知和使用非成像传感器。 1. Energy source or illumination (A) — the first requirement for remote sensing is to have an energy source which illuminates or provides electromagnetic energy to the target of interest. The primary source of electromagnetic energy that illuminates natural targets is the sun, although Earth itself can emit geothermal and man-made energy .Electromagnetic radiation is a form of energy. 1. 能量源或照明——遥感的第一个需求是有一个能够发光的或为感兴趣目标提供电磁能量一个能量源。能够照亮目标的电磁能量的主要来源是太阳，尽管地球本身能够发出地热和人造能量。电磁辐射是能量的一种形式。 The fundamental unit of electromagnetic radiation is the photon. The photon, which has energy but no mass, moves at the speed of light. The wave theory of light has light traveling in wavelike patterns, with its energy characterized by its wavelength or frequency. 电磁辐射的基本单位是光子。光子具有能量但不集中，以光速移动。光波理论是光以波浪形式行进，用波长或频率来表现能量特征。 The speed of light is generally considered to be 300, 000km/ s. Figure 2 shows the electromagnetic spectrum, with wavelengths ranging in size from the very small (cosmi