遥感教程第2部分答案¶
ANSWERS¶
` <>`__2-1: The Niobrara Fm is bright, having the highest average reflectances through the whole spectral interval. In the visible, it has the highest reflectance in the red but reflectances in the green and blue are not much lower, so there is a roughly even mix of the three primary colors, yield dominantly a white with a weak yellowish red overtone. And that is how it looks in the field. The Niobrara typically is a chalky limestone which everywhere, when freshly exposed, is whitish to gray. At the other extreme, the Thermopolis Fm is a black shale and this is indicated by its low reflectances in the visible, having about the same value from blue to red (i.e., a low reflectance, spectrally uniform material is black to dark gray). The Frontier Fm is commonly brownish, but has a greenish member (from the mineral Glauconite); its spectral curve peaks in the green in the visible. The Chugwater Fm has a spectral curve in the visible that rises from low to high reflectance from blue to red - it is thus reddish. In the field, it is a distinctive unit visible for miles away by its medium-red color.**BACK**
` <>`__2-2: 正如前面的答案所说，热电堆是一种黑色页岩。割草机FM的光谱曲线在形状上与热电堆相似，但具有更高的平均反射率。手标本和野外（常有灰黄色风化面）均为中灰色。杰姆砂岩的光谱曲线与白河砾岩相似。因此，它们在可见图像中不容易分离。MSS 7和TM 4采样的近红外段（约0.9 mm）的反射率相差约5%。主要区别在于近红外波段的波长较长。jelm的吸收带分别为1.9和2.3毫米；而White River没有这些吸收带。**BACK**
` <>`__2-3 ：您可能对最多分离4到5或6个单元感到自信。实际上，现场有14个可分离的阵型（或者，在一个阵型中有两个成员）。只有一个单位，这是相当轻的色调，真正站在鲜明的对比，所有其他。其他乐队在分离方面做得更好，我们将在本节后面看到。 `BACK <Sect2_2.html#2-3>`__
` <>`__2-4: 背斜是一种向上的褶皱，岩石呈拱形向上弯曲，顶部是一个顶部，两侧是向相反方向向下移动的倾斜的支腿。向斜是相反的，向下的褶皱，其最低点在中央或槽中。这些褶皱通常是层状的，是三维的。它们倾向于在垂直于最大折叠位置的任何方向上消失或坠落。背斜在褶皱带中逐渐变为向斜（在哈里斯堡的场景中，我们在第1节末尾研究过，山脊主要是受到侵蚀的背斜，因此抗侵蚀的岩石单元在地形上保持在较弱单元之上）。如果你熟悉数学“正弦”曲线图，它的上下曲线序列类似于背斜和向斜。上下水波也具有可比性。我们将在本教程的其他部分中看到这些折叠的图像。 `BACK <Sect2_2.html#2-4>`__
` <>`__2-5: At least four major units are distinguishable. Actually, there are several more formation present but these are either thin and hard to see or occur at the base of the monocline. The black tone in the other aerial photo is actually vegetation, as seen in the foreground of the first color photo.**BACK**
` <>`__2-6: 总的来说，7级更暗。纳瓦霍调频，明亮的高对比度波段1，显示只有轻微的对比度波段7。 `BACK <Sect2_4.html#2-6>`__
` <>`__2-7: 他们都做得很好。但是，颜色混合产品似乎更好地定义和区分图像左2/3和PCA中的单位，其余右上1/3。颜色分配的选择也有助于区分差异，例如，上下Moenkopi成员之间的颜色对比度。 `BACK <Sect2_4.html#2-7>`__
` <>`__2-8: 一些黑色可能是与山脊、台地墙壁等切口相关的阴影；Navajo虚假警报可能是地形的产物-某些切割成岩石的斜坡通常具有不同的特征，可能面对来袭的太阳，这是我们在Morro Bay场景中注意到的效果；冲积层S可能是陡峭山丘底部的岩屑（从悬崖上掉下来的岩屑）的混合物（注意白色部分的位置），两侧高地的斜坡，以及小而通常是干涸的小溪中的漫滩沉积物。Mancos单元向上游突出，包含较少的冲积层，因此Mancos特征占主导地位。 `BACK <Sect2_5.html#2-8>`__
` <>`__2-9: 第一个IDims分类虽然没有彩色或明亮，但似乎优于IDrisi分类。训练场地的精确选择可能是一个因素；场景质量（相对反射率）也可能是一个因素。idrisi和idims中使用了不同的最大似然分类器——也许在idims系统中使用的分类器更为敏感。冬季的IDims图像在质量上（因此准确地说）受到夏季图像的影响，这主要是因为太阳角度较低，不能有效地照亮场景。这些黑色的图案大多是后仰拱侵蚀凹陷处的阴影。 `BACK <Sect2_5.html#2-9>`__
` <>`__2-10: 美国东部大部分地区被森林、草地、农作物或城市地区所覆盖；事实上，据估计，只有不到2%的东部地表由裸露的基岩构成，并且强风化（异常），因此不会出现新岩石。在沙漠中，风化会产生一个薄的风化表面，通常富含铁，覆盖在岩石上（在地表40%以上的地方是露头），因此不同颜色和其他性质的岩石被这种均匀出现的涂层掩盖，使岩石类型的鉴别变得困难。水袋折叠区域的涂层最少。**BACK**
` <>`__2-11: 背斜在构造上和地形上都很高，构成了背斜山脉。向斜是下弯的，在这里，它们占据了山谷，山谷中充满了侵蚀性碎屑（冲积层），这些碎屑是由山间侵蚀冲刷而来的。 `BACK <http://wtlab.iis.u-tokyo.ac.jp/wataru/lecture/rst/Sect2/Sect2_6.htm#2-11>`__
` <>`__2-12: 有一条折叠带斜穿过图像，非常像我们在宾夕法尼亚州中部第一节考试中看到的折叠。在摩洛哥，这些褶皱同样是突出的山脊，因为它们的地层比中间较弱的地层更具侵蚀性。从某种意义上说，这个干旱的阿特拉斯山脉的景色就像宾夕法尼亚州的景色，没有植被的遮蔽作用。 BACK
` <>`__2-13: In the northern half of the mountains that run left-right across the central part of the scene, there is a second strike-slip or wrench fault (part of it is occupied by a dry stream [thin] valley). It, too, is left-lateral, that is, the northern half has moved westward. **BACK **
` <>`__2-14: The Orthris Zone is hard to separate from the juxtaposed Pindus Zone. The Pelagonian Zone shows more topographic variability than the others and has both a valley and a mountain component. This would happen if that Zone were a thrust block that had internal stratigraphic continuity but its lower units were more easily eroded than the upper ones (the mountains to the east). Both zones were likely identified as separate primarily from field evidence, mainly as discontinuities in rock ages (i.e., juxtaposed rocks whose ages indicate some age intervals are missing). **BACK **
` <>`__2-15: A fracture (or joint) is just a crack or break in the rock in which the rock on either side springs apart some small distance. A fault is a break in which the rock on one side slides or slips against the rock on the other side so that each side is displaced some distance from the other. As seen from the air or space, in a photo/image, a fracture is just a linear mark in which the tone of the rocks is the same on both sides. Most faults cause enough movement for individual layers or even formations to be displaced, so that there may be a sharp discontinuity in tonal pattern, in which one type of rock is brought against another. Or, in the China image, topographic parts of a mountain systems are visibly offset by the faulting. **BACK **
` <>`__2-16: This is the way it is done professionally: Place a tissue overlay on the image and trace the fractures as a map. Now, start at any one fracture. Use a protractor to measure the angle it makes with the horizontal, from 0 to 180°. Record that angle. Mark the fracture line with a small cross-mark to indicate you have completed its measurement. Do the same for all other fractures. Place the angles you measure in a table of ranges - thus set up bins like 0 - 5°, 6 - 10°, 176 - 180°. Now make a plot of narrow wedges, each with a 5° angular width, for all of the above intervals from 0 to 180°. Fill in each width to a length set by the number of individual fractures in that angular interval (adopt some unit of length). You will end up with what is known as a "Rose Diagram". To see what this looks like, simply go back to the page you left and scroll down to the bottom of the second figure down. It has two such diagrams. Look at the fractures map and try to correlate their orientation frequencies with the Rose Diagram. **BACK**
` <>`__2-17: You could use a geostationary satellite - one whose orbit is far out and has the satellite's velocity the same as the rotating Earth below, so that it remains "fixed" relative to a point directly below (on the Equator). This sees the Earth at all times of day and night, so the angular illumination effect progressively enhances fracture/faults at different Sun azimuths. Trouble is, at that distance one would need a powerful telescope to get adequate resolution. Or, you could launch an afternoon counterpart to a morning overpass satellite like Landsat, with both travelling in the same orbital sequences but time staggered. However, nobody in NASA (or Congress) would buy this idea unless more uses than just fracture detection can be found to justify the huge expense. **BACK **
` <>`__2-18: In the rose diagram for the West part of the scene, there is a notable trend running north-northwest that isn't picked up by the satellites. This is probably a Sun angle effect - this trend is real but is largely missed owing to illumination bias.**BACK**
` <>`__2-19: The number of fractures (or, more properly, the density, or number per unit area) is less in the Superior province then in the Grenville Province.**BACK**
` <>`__2-20: The Landsat images, even when enlarged, did not clearly demarcate or otherwise bring to view the cross-fracture system. The computer-based edge enhancement technique exposed the presence of these fractures which might have been missed otherwise. Examination of the photos from the aircraft flight could likely have done the same thing but that flight was expensive and really was done ex post facto to corroborate the Landsat evidence. **BACK **