Landsat TutorialWord格式.docx

1、 Return Beam Vidicons and Multi-Spectral Scanner Systems were flown on the first three Landsats. The MSS proved to be a more useful and reliable instrument that the RBV. Landsats-4 and -5 were equipped with an MSS and an improved version of the MSS, the Thematic Mapper （TM）. Landsat-6 carried an Enh

2、anced Thematic Mapper （ETM） only, and Landsat-7 is carrying an Enhanced Thematic Mapper-plus, or ETM+. The operating dates of the Landsat satellites and the instruments on them are listed on Table 1.LaunchedRetiredInstrumentsLandsat-1 （ERTS-1）July 23, 1972January, 1978RBV, MSSLandsat-2January 22, 19

3、75July, 1983Landsat-3March 5, 1978September, 1983Landsat-4July 16, 1982June, 2001*MSS, TMLandsat-5March 1, 1984Landsat-6October 5, 1993ETMLandsat-7April 15, 1999ETM+ Table 1. Landsat Satellites, their Operational Periods, and Their Instruments. * The Landsat-4 sensors were not operational after July

4、, 1987; the satellite was later used for maneuver testing.The data on these CD-ROMs, called the GeoCover data set, cover the United States of America, including Alaska and Hawaii. The data set was produced by the Earth Satellite Corporation for NASA and contains approximately 900 TM images, or scene

5、s. Each Landsat scene is about 115 miles long and 115 miles wide （or 100 nautical miles long and 100 nautical miles wide, or 185 kilometers long and 185 kilometers wide）. This data set covers the United States around 1990 and came from observations acquired by theLandsat-5 satellite. Because of sate

6、llite scheduling constraints and cloud cover obscuring the ground, the scenes in the GeoCover data set were not all observed （acquired） on the same day or within the same month, but include scenes acquired within a year or two of 1990. Within each image or picture, the smallest picture element, or p

7、ixel, covers a square 28.5 meters on a side. No matter how much you zoom in on an image, the smallest square that you can see will be 28.5 meters on a side - even if there are only a few big squares on your screen. That data square is about 94 feet on a side, or an area of about one fifth of an acre

8、 or about 0.08 hectare. The TM pixel size enables observation of large natural features, such as volcanos, rivers, and forests, and large man-made features. Major highways, office buildings （such as the Pentagon or US Capitol building）, city parks and agricultural fields, airports, major bridges and

9、 dams are apparent, but narrow streets, creeks and streams, individual houses, and automobiles cannot be discerned.Since the data are spread over 4 CD-ROMs, the United States was broken up into smaller areas called tiles or mosaics. Collections of tiles were put on each CD - one CD-ROM covers the ea

10、stern United States, another covers the central United States, a third CD-ROM covers the western United States, and one final CD-ROM covers Alaska and Hawaii. Each tile covers an area of 6 degrees of longitude （12 degrees of longitude at latitudes above than 60 degrees, affecting only Alaskan data）

11、by 5 degrees of latitude. A description of the tiling scheme can be found in the GeoCover Product Description Sheet （GeoCover.doc; also Appendix 3.）. Technically speaking, these data were orthorectified （geometrically corrected so that they would appear as they would on a map, always looking straigh

12、t down and not from off to a side）. Then the data were projected （displayed） using the Universal Transverse Mercator projection to minimize the distortion caused by taking a piece of a sphere and flattening it.The TM instrument on Landsat-5 and the ETM+ instrument on Landsat-7 observe the Earth with

13、 7 different filters or bands. Bands 1, 2, 3, 4, 5, and 7 on both instruments are sensitive to light energy from the sun reflected by the surface of the Earth. Each band is sensitive to a different part of the reflected solar energy. The parts of the reflected energy are defined by the length of the

14、 light waves. Thus, band 1 of the TM and ETM+ instruments records reflected light energy only in the range of 0.45 microns （m - a micron is one millionth of a meter long） to 0.52 m. The human eye sees reflected light in that band of wavelengths as the color blue; hence, band 1 is sometimes referred

15、to as the blue band. In a similar manner, bands 2 and 3 of the TM and ETM+ instruments record reflected green and red light, respectively.TM and ETM+ bands 4, 5, and 7 record reflected light in wavelengths that human eyes cannot detect. These bands are referred to as near infrared （NIR, band 4） and

16、short wave infrared （SWIR, bands 5 and 7）.Band 6 of the TM and ETM+ instruments is different from all the other bands because it does not record reflected light energy, but rather heat energy emitted by the EarthIn addition to these bands, the ETM+ instrument also has an eighth band, called the panc

17、hromatic sharpening band. ETM+ band 8 is sensitive to reflected light energy across a broad range of wavelengths that includes blue, green, red and near infrared. This panchromatic band has a spatial resolution of 15 meters, rather than the 28.5 or 30 meters of bands 1, 2, 3, 4, 5 and 7. The sensiti

18、vities of MSS, TM and ETM+ bands are listed in Table 2.BandRBVMSSTM1.48-.57 m green.45-.52 m blue2.58-.68 m red.52-.6 .53-.61 3.69-.83 m IR.63-.69 4.5-.6 .76-.9 m NIR.75-.9 5.6-.7 1.55-1.75 m SWIR60.7-0.8 10.4-12.5 m TIR70.8-1.1 2.08-2.35 2.1-2.35 8.52-.9 m panchromaticTable 2. Landsat Instrument Ba

19、nds. IR = infrared; NIR = near infrared; SWIR = shortwavelength infrared; TIR = thermal infrared （long wavelength）; and m = micron or micrometer.What do the different bands mean to us when we look at the data? To find out what each individual band sees best, or better than the others, check the Land

20、sat-7 images shown in Appendix 2. The individual band images appear as gray scale images - like old-fashioned black-and-white photographs. However, they can be combined to form composite images, with a different gray scale image feeding a different color gun （typically a red-green-blue, or RGB combi

21、nation）. There are many band-color combinations that tell useful stories. Three different and often used composites are summarized below._ True Color: For the true color rendition, band 1 is displayed in the blue color, band 2 is displayed in the green color, and band 3 is displayed in the red color

22、. The resulting image is fairly close to realistic - as though you took the picture with your camera and were riding in the satellite. But it is also pretty dull - there is little contrast and features in the image are hard to distinguish. False-Color, also called Near Infrared or NIR: In this image

23、, band 2 is displayed in blue, band 3 is displayed in green, and band 4 is displayed in red. This rendition looks rather strange - vegetation jumps out as a bright red because green vegetation readily reflects infrared light energy! It is similar to pictures taken from aircraft when using infrared f

24、ilm and is very useful for studying vegetation._ Short-Wavelength Infrared, or SWIR: In this SWIR image, band 2 is displayed in blue, band 4 is displayed in green, and band 7 （or 5） is displayed in red. This rendition looks like a jazzed up true color rendition - one with more striking colors. This

25、is the band combination was used in the GeoCover data set. It is built into the GeoCover data and cannot be changed. Further, the contrast and brightness have been altered in the GeoCover data set to make a more consistent overall mosaic.The appearance of different surface features for the different composite images is summarized on Table 4.True Color Red: Band 3Green: Band 2Blue: Band 1False Color Band 4SWIR （GeoCover） Band 7Trees and bushesOlive GreenRedShades of greenCropsMedium to lig