遥感教程简介答案¶
答案¶
` <>`__|image0|I-1: The eye shares functions common to a camera. To the left is a diagram of the human eye. Key components are the cornea, the iris and pupil, the lens, and the retina. Light from objects close to distant pass through the outer layer, or sclera, of the eye into the cornea which encloses a liquid, the vitreous humor whose index of refraction is 1.3 (air is 1.0). Refraction (bending) of light occurs in the cornea, and is diverted inward to pass through the iris (which has some distinctive color, which varies in individuals according to precise composition of a pigment). The iris responds to varying amounts of light (brightness) by diameter changes of the pupil (as it enlarges, more light is admitted). This refracted light now passes through the lens, a transparent material that serves to focus light; light is further refracted as it passes across the curved boundaries. Focusing is done by changing the shape (thickness) of the lens through the action of the ciliary muscle; in a thickened mode, the lens focuses near objects. These changed light rays now pass through the gelatin-like vitreous humor onto the retina which can detect rays extending against a hemisphere more than 180° in arc. Most of the focused light strikes within 20° of a central point called the fovea. The retina (somewhat analogous to camera film) consists of layers that include nerve cells and light receptors called cones and rods. Individual cones, in a central region called the macula, are receptive to red, green, or blue light (because of pigments sensitive to each); the rods are tuned to variations in brightness and respond by sending signals in shades of gray. The processed light is converted to electrical impulses that move to the optic nerve (itself about 20° off center, in the eye's blind spot) and eventually to the brains visual center, where the inverted image on the retina is converted to upright and the color and brightness signals are combined to yield what the eye perceives to be an image of the external world. (Note: the eye lens focuses by changing thickness; the camera by forward/backward movements). Human vision extends from a spectral region (the visible) that covers wavelengths of 400 to 700 nanometers (a nanometer is 10-9, or a billionth, of a meter). Under contrasting conditions, the eye is capable of seeing a line 2 millimeters wide at a distance of 5 meters. **BACK **
` <>`__I-2: Acquisition/measurement; data/information; properties; phenomenon,...material; recording device; not in contact; measuring fields.radiation; instruments. **BACK**
` <>`__I-3: Geospatial connotes the distribution of something in a geographic sense; it refers to entities that can be located by some co-ordinate system. The three terms "feature; object; class" have different but somewhat overlapping meanings. Feature can refer to "overall appearance", "mark", or "characteristic", and/or to a set of measurable properties, or, more narrowly, to a specific geometric or geomorphic entity on the surface of a planet such as Earth. Object relates to a single entity, of a physical nature, capable of being sensed (e.g., seen or touched), to which a descriptive name can be given, such as "house", "road". Class has a more general connotation, pointing to a group of features or objects of identical or similar types that have taxonomic significance; examples are "forest"; "urban"; "mountains". Classes can be hierarchical, that is, can be subdivided into subclasses; thus "urban" includes "inner city/suburbia", road networks", "neighborhoods", "shopping centers", etc. The term "theme" is often interchangeable with "class". **BACK**
` <>`__I-4: One might think there is an error, at first glance. The delta E on the left denotes a change in energy level. As an equation, there should be a delta variable on the right, in this case "v" (this is the letter "vee" which here is similar in appearance to the small Greek letter "nu" [n] that was not available on the html editor; some textbooks use the letter "f" for frequency). This seems to give an inconsistency in which both E and delta E = hv. But, in effect, this is "built in" to the meaning of the equation: when there is a change in energy level, as for example an orbiting electron in an atom moving to a higher energy state, this change is represented by some delta E which has its characteristic frequency. For the formula: E = hv, at some energy level, there is a corresponding frequency at some value unique to the discrete energy value for that particular E. **BACK **
` <>`__I-5: 简单地说，“越长越低”，这意味着较长的波长与较低的能级有关。因此，“越短越高”。 **BACK**
` <>`__I-6: The appropriate equation is E = hc/wavelength, or Wavelength (in meters) = hc/E. Thus, Wavelength = (6.626 x 10-34) (3.00 x 108)/(2.10 x 10-19) = 9.4657 x 10-7m = 946.6 nm; = 9466 angstroms; = 0.9466 µm (in the near-infrared region of the spectrum). **BACK**
` <>`__I-7: Here the operative equation is: Wavelength = c/frequency. Thus, Wavelength = (3.00 x 108) (120 x 106) = 2.5 meters. **BACK**
` <>`__I-8: 1000纳米/微米；10000 A/微米。 **BACK**
` <>`__I-9: (Intervals in micrometers). 1) Visible-Near IR (0.4 - 2.5); 2) Mid-IR (3 - 5); 3) Thermal IR (8 - 14); 4) Microwave (1 - 30 centimeters). **BACK**
` <>`__I-10: Go first to the peak close to 500 nanometers of the irradiance curve for sunlight as it reaches the outer atmosphere. On the ordinate, its spectral irradiance reads 2100. For the sea level irradiance curve at the same peak position, the value is estimated to be 1300. Thus, the percent loss is: (2100 - 1300)/2100 x 100 = 38%. Note that at most other spectral locations, the loss is less. **BACK**
` <>`__I-11: (in micrometers) a) 0.8 - 0. 95; b) 0.8 - 0.95; the percent reflectance is less than grasslands; c) 0.59; d) 0.57. The four classes should be distinguishable at 0.6 micrometers, provided the instrument's sensitivity (ability to distinguish reflectances of small differences) is 5% or better. **BACK**
` <>`__I-12: 在可见光中，红砂（一种岩石材料）比任何一种植被类型（也包括水）都亮；但是一些岩石可能更暗（如黑色页岩）。在这些曲线中，这种情况在近红外波段（1.2微米）发生逆转，因此在近红外波段的这一部分，与大多数岩石类型相比，植被通常会更亮（这里，松林更亮）。 **BACK**
` <>`__I-13:By extrapolating to the abscissa and ordinate, the values for 0.5 and 1.1 micrometers respectively are a) water:10 and 1; b) rock (sand): 40 and 32; c) grasslands: 20 and 40. When these are plotted in the diagram, both rock and vegetation are about equidistant from the unknown X. This is a case where one might choose a different wavelength. Try 1.0 micrometers and see if discriminating between those two classes improves. The conclusion you should now reach is a strong argument for having larger numbers of spectral bands (each can also cover a narrower interval of wavelengths) on the sensor. **BACK**
` <>`__I-14: In a false color composite, for example, the forest and growing crops are likely both to appear red (we will find out why later in this section). But, in an image most fields tend to have straight boundaries - usually rectangles - whereas forests commonly are irregular in shape and distribution. Shape is a prime tool by which an interpreter can distinguish classes that have similar spectral characteristics but are distinct in their outlines. Look at the Salt Lake City image again - note the widespread forests in the mountains and the small, regularly-shaped fields in the lowlands. **BACK**
` <>`__I-15: 对于非植被类，在~0.87微米处；在~0.78微米处。 **BACK**
` <>`__I-16: The gray levels will depend on the specific point locations you chose. As a general rule, a feature or object or patch seen in a filtered aerial black and white photo (or a space image) will be light-toned if its color is close to that of the filter's color, and will be varying levels of darker in images made with other colors depending on color proximity in the visible light scale (red is spectrally farther from blue than from green). **BACK**
` <>`__I-17: The white feature is light (clear-toned) in all three color layers (or projections) and represents a white object, such as light sand, on the ground. The blue represents materials that are brightest in shorter wavelengths and diminish in reflectance in longer visible wavelengths, such as may be the case for soils and some rock materials. Dark red is typical of trees and thick shrubs; light red associates with grass cover (also, early leafing or even certain plant disease). **BACK**
` <>`__I-18: This is an example of what I call a "subjective" question in which no specific answer can easily be given owing to the particular choices of feature, location, etc. Hereafter, I will treat similar questions and their answers with the simple statement: Subjective. However, the red tones in the f.c. composite in this scene are medium gray in the bottom black and white photo but dark in the other two. **BACK**
` <>`__I-19: 13,300 sq. miles; 33,225 sq. km; 8,512,000 acres. `**BACK <Part2_150.html#I-19>`__ **
` <>`__I-20: 探测器本质上是电子的，当任何特定数量的光子击中每个探测器（在同一时间内）时，它们往往会做出相似的反应。但是，它们并不完全匹配。因此，当多条扫描线穿过同一地面特征时（假设光谱均匀性），它们的响应可能稍有不同，从而导致图像中的灰度从一个到另一个有区别的变化。这有助于找出单个扫描行。有时，一个给定的探测器也会在其正常模式的响应中经历波动，因此，在其整体特征变化中，测线可能比相邻的两条测线更亮或更暗。计算机处理可以最小化差异，这样正确处理的图像看起来几乎没有单独的线条（红色与蓝色的距离比绿色的距离远）。 **BACK**
` <>`__I-21: Subjective. But, at the least you should have found Trenton, New Jersey. **BACK**
` <>`__I-22: 第4波段相当“褪色”，因为它显示了整体最暗的色调，对比度很小。但是，它最能显示海水中的淤泥。波段5显示了最清晰的对比度（灰度的最大扩散）。植被呈现最深的灰色。这些色调强调了这个波段图像左上角的脊线。在4号和5号中，松荒地都有点暗；这说明有相当多的常绿植物，有着较暗的针叶。6波段以光调为主，说明高反射植被分布广泛。黑暗地带是城市地区。从接近零度的反射来看，这条带和7号带中的水是非常暗的。第7波段以更轻的音调标记。6号和7号都显示了暗一点的藤条，这表明常绿植物比落叶树反射的少。值得注意的是，尽管这些山脊与其间植被丰富的山谷几乎没有对比，但它们还是可以被辨别出来。同样要注意的是，城市在4级和5级中并不突出。 **BACK**
` <>`__I-23: 主观的。您应该已经发现表的标准能够很好地工作。 **BACK**
` <>`__I-24: 对于以1:1000000的比例打印的完整场景（标准产品，侧面约10英寸，带白边），TM和MSS产品显示出很强的相似性，即使在细节上也是如此。这是因为与79米的MSS相比，30米处添加的像素（代表地面上的区域）的效果在TM图像中没有明显不同。对于在侧面延伸超过7英寸的这一比例的图像，对于79米的情况，像素的大小为79/185000 x 7=0.003英寸（185000表示场景的地面等效长度为185公里）。30米的外壳提供0.001英寸的像素尺寸。眼睛无法清楚区分这两种尺寸。当比例变大（1:250000生成28英寸宽的完整图像）时，高分辨率TM图像会产生明显的改善，像素仍然足够小（0.004英寸），不会分散到眼睛的注意力（但79米长的MSS的像素为0.012英寸，因此可以看到像素并给出微小但令人不安的块状效应）。同样地，当从TM数据生成次新图像（完整图像的一部分）时，以某种典型尺寸（例如10英寸）打印时，它也会显得更清晰。 **BACK**
` <>`__I-25: 由于在一个类别中出现的个别材料（例如，一个矿物群中的几种矿物）在光谱曲线连续体中表现出它们在成分上的细微变化，因此高光谱传感器不仅能够很好地识别不同的组，而且能够检测到rmine是此类组中单个成员的身份。 **BACK**
` <>`__I-26: 更明显的区别是具有强烈三维表达的特征形状的扭曲，如山脉。在Landsat的图像中，旧金山附近的山脉（你可以通过看封面上的彩色图像来快速查看这些，这显示了圣弗朗西索；或者你可以跳到前面，看到第6-9页上的一个类似的场景）出现“正常”，也就是说，它们在山坡的两侧有斜率相似的斜率。但是，在雷达图像中，一个斜坡的一边看起来是伸展的，另一个斜坡看起来是缩短的；这是雷达图像的一个标志，称为“中途停留”。第二个差异与灰色色调水平有关。在雷达中，有些特征具有音调特征，这与在红外图像附近可见的陆地卫星的音调特征非常不同，其原因在第8节中有介绍。一个很好的例子是旧金山机场，它的雷达是相当黑的，但是在Landsat的大部分波段里都会有各种各样的灰色。 **BACK**