实习一指导书Word格式文档下载.docx

1、 The most useful for this class is accessed by clicking on the little question mark （?） on the upper right side of the ENVI interface. Opening Images （打开影像）1）Start ENVI.2）Lets open a Landsat Thematic Mapper （TM） image in folder“TM20080802”. Click as this following figure show.3） In this folder is a

2、folder called “SCENE01”, in this folder, choose “header.dat” and click OK. It should open. 4） Open an image in gray scale （灰度影像）. In the “available band lists”, choose any one band, click “gray scale” which is a default option, and click “load band”, then this image is showing in three windows, one

3、is for image, one is for scroll, one is for zoom.Now lets open a second window so that you can display two images side by side. Choose another one band, and click “No Display”, choose “New Display” , click “Load Band”, then this image is showing in another three windows 5） open an image in RGB Color

4、 （彩色影像）. Choose option “RGB Color” which is next to option “Gray Scale”. Then choose one band for channel R, another one band for Channel G, and another one for Channel B, then click “load band”6） Changing the Color Scheme （改变配色方案，即选择不同的波段分别赋给R、G、B三个通道，查看合成结果）The appearance of an image depends on ho

5、w you choose to assign the three additive primary colors （red, green and blue） to satellite image bands （also called spectral bands or channels）. The convention is to assign whichever spectral band corresponds to near infrared （NIR） to the color red. The TM image that you are using has 7 spectral ba

6、nds, numbered 1 7, each of which has captured a different part of the electromagnetic spectrum. Now you will try to change the bands that are assigned to the primary colors to make the image look like what you would see with your eye （or with a conventional camera）. Notice that there are various con

7、trols for changing the appearance of images. Experiment with various band combinations with the goal of making an image look like it would look to your eye. Note that any standing water will be dark, vegetation will be greenish. On the worksheet, record the band to primary color combinations that re

8、sult in “true color.” Getting Information about an Image （获取影像信息）Often you need to gather basic information about image files. First, some terminology:“Raster” is the technical term for image or GIS data that are composed of pixels arranged in rows （or lines or records） and columns （or samples）. Eac

9、h x,y （row, column） grid cell is called a “pixel” （just like in your digital camera）. （栅格数据）“Vector” is the technical term for GIS point, line, and polygon data in computer （digital） format. Vector data are composed of the x,y coordinates of points and information about if and how the points are con

10、nected into lines or areas （polygons）. （矢量数据）A layer in ENVI is either a single raster satellite band or a vector dataset. （ENVI中图层可以是栅格也可以是矢量）A file （e.g. an image file） can have one or several layers. （一个影像文件中可有一个或多个图层）Get the map information: Click in front of “map info” in “available band list”,

11、 then you will see the map information for this image. Read carefully so that you can answer the worksheet questions. （获取地图信息）Right Click on the Layer Info icon at the top of your “available band lists” and choose “Edit Header”. A window will open that includes some basic information about this file

12、, including the number of layers （bands）, the number of columns （width） and rows （height）, the type of data.（查看文件的基本信息）Right Click on the Layer Info icon at the top of your “available band lists” and choose “Quick Stats”. After a few minutes, a window will open that includes some basic information a

13、bout this file, including the minimum, maximum and mean pixel values and other information for each band. Explore some of the tabs on this information window （and answer the worksheet questions）. （查看文件的统计信息）Linking and Unlinking Images in Separate Graphics Windows （影像关联及解除影像关联）It is often useful to

14、“Link” viewers together so that you can identify the same location in two or more images. Go back to your “Available band list”, click two different bands one by one and display them in two different windows. In any one image, click as the following figure show:（基于像素的关联）A window displayed as:Click O

15、K, then those two images linked.Click Cursor locations/value as the following figure show:If your images are linked, red rectangles will appear in both images （if they arent linked the white cross will only appear in the active image） and a window will pop up that contains information about the exac

16、t pixel at the intersection of the rectangles. Move the rectangle around with your mouse and note that it moves in both images. The above method is a link based on image pixel. Please try to link to image based on geographical locations. （基于地理位置的关联）Worksheet: Lab 01: Introduction To ENVI （作业，要求每个题在必

17、要的地方要截图，对结果仔细分析后回答问题）1. What are the roles of the three different windows for one image? （影像显示时，三个不同窗口的作用是什么？）答：there are three windows, one is for image, one is for scroll, one is for zoom.1.Main Image Window（主影像窗口）主图像窗口是由一幅以全分辨率显示的图像的一部分组成。该窗口在你第一次载入一幅图时自动地被启动。2.Scroll Window （滚动窗口）滚动窗口是一个以二次抽样的分辨

18、率显示大图像的小图像显示窗口。只有要显示的图像比主图像窗口以全分辨率能显示的图像大时，才会出现滚动窗口。3.zoom Window（缩放窗口） 缩放窗口是一个晓得图像显示窗口，它以用户自定义的缩放系数使用象元复制来显示主图像窗口的一部分。2. What is the projection of this image? what is the pixel spatial resolution? （给定影像的投影方式是什么？空间分辨率是多少？横轴墨卡托投影 分辨率为 25米3. Describe the TM image that you originally opened using the s

19、tandard false color composition（标准假彩色合成） （in an RGB image, Band 4 （近红外波段）for channel R（红通道）, Band 3 （红波段）for channel G（绿通道）, Band 2 （绿波段）for channel B） （蓝通道）. （影像的彩色合成）a. What color is the vegetation surrounding town? Why? （城区外围植被是什么颜色，为什么？红色植被在近红外和红外波段的反射特性，-R，所以是红色。b. What color is the water body?

20、 （水体是什么颜色，为什么？黑色水体在近红外波段反射率几乎为零4. Describe the TM image that you originally opened using another false color composition（另一种假彩色合成） （in an RGB image, Band 5 for channel R, Band 4 for channel G, Band 3 for channel B）. （影像的彩色合成）绿色，在近红外波段植被反射设置为绿色b. What color is water body?理由如3-2，水体在近红外波段反射率几乎为零5. What

21、 band and color combinations are required to make the image look like what your eye would see （“true color”）? （如何合成一景真彩色影像？） 绿色植被绿色设置正确蓝色水体蓝色设置正确。c. Please make a comparison of the vegetation color, water body color based on the results from questions 3,4 and 5. （对3，4，5中植被、水体的颜色作一个对比. ）3，4水体都是黑色，而5是

22、蓝色，水体在除蓝色以外波段吸收巨大，几乎不反射。6. Based on the Layer Information window provide the following information about the TM image file: （TM影像的相关信息）a. How many bands does the image have? （影像有几个波段？7个b. What is the mean pixel value for Band 4? （第4个波段像素DN值的平均值是多少？106.119806c. What is the minimum pixel value for Ban

23、d 2? （第2个波段像素DN值的最小值是多少？） 0 d. What is the histogram for all bands like in this image? （显示该影像所有波段的直方图。7. Link band 2 and band 6 based on geographical locations: （基于地理位置对波段2和波段6进行关联）a. What are the DN values of water body surrounding forbidden city in band 2 and band 6? （波段2和波段6中紫禁城外水体的DN值各是什么？波段2是32

24、，波段6为138b. What are the DN values of vegetation in Tiantan Park in band 2 and band 6? （波段2和波段6中天坛公园植被的DN值各是什么？波段2为36 波段6为142Lab 02: Converting Radiance to Reflectance（辐射率到反射率的转换） Note that there is a worksheet at the end of this lab write-up that you must turn in at the end of the lab period. （实验后有一

25、些问题，完成这些问题，并于是实习结束后上交）Today we will use some ENVI tools to convert what the satellite measures, called radiance, to the characteristic ability of materials on the ground to reflect light （reflectance）. There are many concepts in todays lab that we have discussed in much more detail in the past few w

26、eeks, remembering that reflectance is NOT directly measured by satellites and must instead be calculated.First, some definitions:Digital Number （DN） the unitless integer that a satellite uses to record radiance （e.g. 0 255 where 0 = no radiance and 255 = some maximum amount of radiance that the sens

27、or is sensitive to）. Each image pixel has one DN for each band. （DN值）Radiance （L） the amount of light received at a particular place, in this case a satellite （watts/m2/sr）. （辐射率）Irradiance （E） the amount of incoming light from the sun （either at the ground or at the top of the atmosphere （TOA） （wat

28、ts/m2）. （入射辐射）Reflectance （r） the amount of light that reflects off of something divided by the amount of incoming light （often given as a fraction or a percent）. （反射率）Transmittance （t） the proportion of light that is transmitted through something （e.g., through the earths atmosphere）, usually given as a fraction. （透过率）The fundamental task in remote sensing is distinguishing objects （e.g., plants, rocks） or properties （e.g., plant leaf nutrient content） on earth, based on the amount o