EnglishforITandEE-15概要.ppt

Technical English For Information Science and Electronic Engineering Unit 15 Remote Sensing Part I An Overview of Remote Sensing New Words New Words New Words 1 The technology of modern remote sensing began with the invention of the camera more than 150 years ago. Although the first, rather primitive photographs were taken as “stills” on the ground, the idea and practice of looking down at the Earth’s surface emerged in the 1840s when pictures were taken from cameras secured to tethered balloons for purposes of topographic mapping. 1 Perhaps the most novel platform at the end of the 19th century is the famed pigeon fleet that operated as a novelty in Europe. By World War I, cameras mounted on airplanes provided aerial views of fairly large surface areas that proved invaluable in military reconnaissance. From then until the early 1960s, the aerial photograph remained the single standard tool for depicting the surface from a vertical or oblique perspective. 2 Satellite remote sensing can be traced to the early days of the space age and actually began as a dual approach to imaging surfaces using several types of sensors from spacecraft. With the emergence of the space program in the 1960s, Earth-orbiting astronauts acted much like tourists by taking photos out the window of their spacecraft. 3 The term “remote sensing” is now commonly used to describe the science, and art, of identifying, observing, and measuring an object without coming into direct contact with it. This process involves the detection and measurement of radiation of different wavelengths reflected or emitted from distant objects, by which the objects may be identified and categorized by class, substance, and spatial distribution.1 4 Radiation Unless it has a temperature of absolute zero (?273?C) an object reflects, absorbs, and emits energy in a unique way, and at all times. This energy, called electromagnetic (EM) radiation, is emitted in waves that are able to transmit energy from one place to an