影像介绍

Contents:

• Collection Descriptions    
  • Aerial        
  • ASTER        
  • EO-1        
  • Landsat Archive        
  • GLS        
  • Landsat MRLC        
  • Landsat Legacy        
  • MODIS Aqua        
  • MODIS Terra        
  • MODIS Combined        
  • TerraLook    
• About Browse Images    
  • ASTER Level 1A, Level 1B, and Level 1T        
  • EO-1 ALI        
  • EO-1 Hyperion        
  • GLS1975 (Landsat 1-3)        
  • GLS1975 (Landsat 4-5)        
  • GLS1990
  • GLS2000        
  • GLS2005        
  • GLS2005 - Islands (EO-1)        
  • GLS2010        
  • GLS2010 - Islands (EO-1)                 
  • Landsat 1-5 MSS        
  • Landsat 4-5 TM        
  • Landsat 4 - Present        
  • Landsat 7 ETM+        
  • Landsat 7 ETM+ SLC-off        
  • Landsat 8 OLI        
  • Landsat 8 OLI Pre-WRS-2        
  • MODIS        
  • MRLC 2001 Terrain Corrected (TC) and 2001             Reflectance Adjusted (RA)        
  • National Aerial Photography Program (NAPP)        
  • North American Landscape Characterization (NALC)        
  • National High Altitude Photography (NHAP)        
  • Systematic ETM+ L1G        
  • TerraLook        
  • Tri-Decadal ETM+ (1999-2003)        
  • Tri-Decadal ETM+ Pan (1999-2003)        
  • Tri-Decadal ETM+ Pan Mosaics            (1999-2003)        
  • Tri-Decadal TM (1987-1997)        
  • Tri-Decadal TM Mosaics (1984-1997)        
  • Tri-Decadal MSS 4-5 (1982-1987)        
  • Tri-Decadal MSS 1-3 (1972-1983)    
• Frequently Asked Questions (FAQs)    
  • How is the cloud cover calculated, and            why are some scenes cloudy when the cloud cover is reported to            be 0%?        
  • Why are some Landsat scenes            missing?        
  • Can I find the actual            gain and bias values for a Landsat scene on GloVis?        
  • Where can I find out more about            Landsat MSS, TM, ETM+, and OLI data?        
  • Does red in ASTER images always            represent vegetation?        
  • Why do some ASTER images have a            ‘smeared‘ line in them?        
  • Why are some ASTER images completely            white?        
  • Why are some ASTER L1A images            missing?        
  • Why does the EO-1 Scene ID list            a path and row that is different than the path and row of            the center part of the image?        
  • If NAPP scenes cover a square area,            why do they appear rectangular in GloVis?        
  • When I download a NALC            dataset, will I receive all of the images for that triplicate?        
• Contact Customer Services    

Collection Descriptions

Note: Download available denotes that the actual data product is available for download at no charge through GloVis.

About Browse Images

All of the USGS browse images are subsampled JPEGs of selected bands from the actual sensor data. The band combination, stretch, and resolution of the browse vary according to each sensor. Scenes from the Landsat archive are processed to Standard Terrain Correction (Level 1T). While some scenes do not have the ground-control or elevation data necessary to perform L1T correction, the best level of correction is applied. More details at the Landsat page, under Product Information.

Within the Browse Image Viewer, the browse images are displayed in Lambert Azimuthal Equal Area Projection unless otherwise noted.

• ASTER Level 1A, Level 1B, and Level 1T

  • The ASTER instrument has 3 telescopes which are independently            turned on and off. Visible Near Infrared (VNIR) and Shortwave            Infrared (SWIR) bands are typically turned on for Day acquisitions.            Thermal Infrared (TIR) bands may be available for Day- and            Night-acquisition images.            The VNIR telescope has a 15 meter resolution, but the VNIR            Full Resolution Browse have a 30 meter resolution since they            may include a band from the SWIR telescope. The TIR telescope            and TIR Full Resolution Browse have a 90 meter resolution.            The TIR browse displayed on GloVis are from selected            night-acquired images.            SWIR images after 4/1/2008 are saturated            and therefore should not be used.            Please review the metadata for each granule you select to            determine what bands are available for that granule.        
  • GloVis provides a catalog of ASTER Level 1A browse images            for the entire world and ASTER Level 1B and Level 1T browse images            for the U.S. and territories.            The following data sets are orderable from GloVis:        
    • ASTER Level 1A contains reconstructed,            unprocessed instrument digital numbers (DNs) derived             from the telemetry streams of the three telescopes: VNIR, SWIR,            and TIR. Each browse image is only available if the corresponding            telescope was turned ON.            ASTER VNIR browse images are displayed as a 3N, 2,1 (RGB)            color composite.            ASTER TIR browse images are displayed as a band 13,12,10 (RGB)            color composite.            While ASTER Level 1A browse are available for searching and viewing,            ASTER Level 1A products are available through GloVis only to            authorized users, as described on the             ASTER Policies page.        
    • ASTER Level 1B            browse use the ASTER Level 1A browse images. Level 1B granules are            available through GloVis only over the United States and            territories for all of the channels acquired previously through the            telemetry streams of the three different telescopes in Level 1A.        
    • ASTER Level 1T is a multi-file product            that contains radiometrically calibrated and geometrically            co-registered data with terrain and precision correction applied.            When the Global Land Survey epoch 2000 (GLS2000) ground control            points (GCPs) or elevation data necessary to perform terrain and            precision correction are unavailable, the best achievable level            of correction is applied, and the level of correction documented            in the metadata. AST_L1T scenes are rotated north up and are            provided in the Universal Transverse Mercator (UTM) projection.            To acquire AST_L1T science data and GeoTIFF imagery in the            visual spectrum, the VNIR telescope must be ON, and for the            thermal spectrum, the TIR telescope must be ON. ASTER Level 1T            scenes/granules acquired over the United States and territories            are available through GloVis.        
  • Please refer to the             ASTER Policies page            for more information about ordering.    

  Users are advised that ASTER SWIR data acquired from late April 2008    to the present exhibit anomalous saturation of values and anomalous    striping. This effect is also present for some prior acquisition    periods. Please refer to the ASTER SWIR User Advisory Document for more details.    

   

   

• EO-1 ALI

  • The Advanced Land Imager (ALI) browse images are generated from the            Level 1 radiometrically corrected data and displayed as a 5,4,2             (RGB) band combination.         
  • Pixels are subsampled to a resolution of 240 meters from the             original 30-meter data (a factor of 8 in each direction).        
  • The exact scene length will vary.  The two most typical scene            lengths will be approximately 42 km for a standard scene and            approximately 185 km for an extended scene.        
  • Each band is linearly stretched between the 1% and 97% histogram             values.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 25K.  For the 1000 meter display mode,            the browse images are GIFs with an average file size of 6K.        
  • In the "Show Browse" window, browses            are Level 1 radiometrically corrected in satellite orientation.            Level 1T provides radiometric, systematic and geometric corrections            incorporating ground control points that are applied while            employing a 90-meter Digital Elevation Model (DEM) for topographic            accuracy. Geodetic accuracy of the product depends on the accuracy            of the ground control points and are expected to be within 2 pixels.            Scenes that do not have adequate ground control will be processed            to the best level of correction (L1Gst). L1Gst provides systematic            terrain correction in 16-bit radiance values.            L1T scenes are available in GeoTIFF format.    

   

• EO-1 Hyperion

  • The Hyperion browse images are generated from the Level 0 (raw)             data and displayed as a RGB (40:31:13) band combination.        
  • Pixels are subsampled to a resolution of 120 meters from the             original 30-meter data (a factor of 4 in each direction).        
  • The exact scene length will vary.  The two most typical scene            lengths will be approximately 42 km for a standard scene and            approximately 185 km for an extended scene.        
  • The Hyperion browses have had the dark calibration subtracted and             the gains have been applied.  Each band is linearly stretched             between the 1% and 97% histogram values.  The data is then scaled             from 12 bits to 8 bits.        
  • For the 120 meter display mode, the images are JPEG compressed            with an average file size of 25K.  For the 1000 meter display mode,            the browse images are GIFS with an average file size of 2K.        
  • In the "Show Browse" window, browses            are Level 1 radiometrically corrected in satellite orientation.            Level 1T provides radiometric, systematic and geometric corrections            incorporating ground control points that are applied while            employing a 90-meter Digital Elevation Model (DEM) for topographic            accuracy. Geodetic accuracy of the product depends on the accuracy            of the ground control points and are expected to be within 2 pixels.            Scenes that do not have adequate ground control will be processed            to the best level of correction (L1Gst). L1Gst provides systematic            terrain correction in 16-bit radiance values.            L1T scenes are available in GeoTIFF format.    

   

• GLS1975 (Landsat 1-3)

  • Images acquired from 1972-1983 are displayed as a 4,2,1            (RGB) color composite.         
  • Pixels are subsampled to a resolution of 480 meters from the            original 80-meter data.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 38K. For the 1000 meter display            mode, the browse images are GIFs with an average file size of 23K.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.     

   

• GLS1975 (Landsat 4-5)

  • Images acquired from 1982-1987 are displayed as a 4,2,1            (RGB) color composite.         
  • Landsats 4-5 MSS data has sparse coverage and was used only to fill            in gaps in coverage for the GLS1975 Landsat 1-3 dataset.        
  • Pixels are subsampled to a resolution of 480 meters from the            original 80-meter data.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 38K. For the 1000 meter display            mode, the browse images are GIFs with an average file size of 23K.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.     

   

• GLS1990

  • Images acquired from 1987-1997 are displayed as a 5,4,3            (RGB) color composite.         
  • Pixels are subsampled to a resolution of 480 meters from the            original 30-meter data.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 38K. For the 1000 meter display            mode, the browse images are GIFs with an average file size of 23K.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.     

   

• GLS2000

  • Images acquired from 1999-2003 are displayed as a 5,4,3            (RGB) color composite.         
  • Pixels are subsampled to a resolution of 255 meters from the            original 30-meter data.         
  • Each Landsat 7 scene is color-stretched based on individual            scene content. This may result in an apparent mismatch of            colors between scenes.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 147K. For the 1000 meter display            mode, the browse images are GIFs with an average file size of 8K.        
  • Full-resolution GeoTiff data may be downloaded at no charge.     

   

• GLS2005

  • Images acquired from 2003 - 2008 are displayed as a 5,4,3            (RGB) color composite.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 147K. For the 1000 meter display            mode, the browse images are GIFs with an average file size of 8K.        
  • Full-resolution GeoTiff data may be downloaded at no charge.     

   

• GLS2005 - Islands (EO-1)

  • Images acquired from 2004 - 2008 are generated from the            Level 1 radiometrically corrected data and displayed as a 5,4,2             (RGB) band combination.         
  • Pixels are subsampled to a resolution of 240 meters from the             original 30-meter data (a factor of 8 in each direction).        
  • The exact scene length will vary.  The two most typical scene            lengths will be approximately 42 km for a standard scene and            approximately 185 km for an extended scene.        
  • Each band is linearly stretched between the 1% and 97% histogram             values.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 25K.  For the 1000 meter display mode,            the browse images are GIFs with an average file size of 6K.        
  • The "Show Browse" images (viewed in a separate browser window)             are Level 1 radiometrically corrected browse in satellite            orientation.        
  • Full-resolution GeoTiff data may be downloaded at no charge.     

   

• GLS2010

  • Images acquired from 2008 - 2011 are displayed as a 5,4,3            (RGB) color composite.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 147K. For the 1000 meter display            mode, the browse images are GIFs with an average file size of 8K.        
  • Full-resolution GeoTiff data may be downloaded at no charge.     

   

• GLS2010 - Islands (EO-1)

  • Images acquired from 2009 - 2011 are generated from the            Level 1 radiometrically corrected data and displayed as a 5,4,2             (RGB) band combination.         
  • Pixels are subsampled to a resolution of 240 meters from the             original 30-meter data (a factor of 8 in each direction).        
  • The exact scene length will vary.  The two most typical scene            lengths will be approximately 42 km for a standard scene and            approximately 185 km for an extended scene.        
  • Each band is linearly stretched between the 1% and 97% histogram             values.         
  • For the 240 meter display mode, the images are JPEG compressed            with an average file size of 25K.  For the 1000 meter display mode,            the browse images are GIFs with an average file size of 6K.        
  • The "Show Browse" images (viewed in a separate browser window)             are Level 1 radiometrically corrected browse in satellite            orientation.        
  • Full-resolution GeoTiff data may be downloaded at no charge.     
      

   

• Landsat 1-5 Multispectral Scanner (MSS)        

  • For Landsat 4 and 5 MSS, the images are displayed as RGB            composites, bands 4, 2, and 1, with a 2% linear stretch. For            Landsat 1, 2, and 3 MSS, the RGB composites are created from bands            7, 5, and 4.         
  • Images are resampled to a pixel size of 240 meters from the             original nominal 80-meter data.         
  • In the "Show Browse" view, the MSS images may appear to be            one-fourth the size of the Landsat 7 browse images because of the            processing used to create the browse, but the actual MSS scene will            cover approximately the same area (185 x 170 km).        
  • In the 240-meter display mode, browse images are JPEG compressed             files with an average file size of ~50K. For the 1000-meter display            mode, the browse images are GIFs with an average file size of ~35K.    

   

• Landsat 4-5 Thematic Mapper (TM)

  • The images are displayed as RGB composites, bands 5, 4, and 3, with            2% linear stretch applied.        
  • Images are resampled to a pixel size of 240 meters from the            original 28.5-meter data.        
  • In the "Show Browse" view, the Landsat 4 and 5 browse            images may appear to be one-fourth the size of the Landsat 7 browse            images because of the processing used to create the browse, but the            actual TM scene will cover approximately the same area (183 x 170            km).        
  • In the 240-meter display mode, browse images are JPEG compressed            files with an average file size of ~50K. For the 1000-meter display            mode, the browse images are GIFs with an average file size of ~35K.        
  • The browse previews that are used to create the            "Show Browse" display are uncorrected images in satellite            orientation, and they can be viewed in a separate window.    

   

• Landsat 4 - Present (MSS,        TM, ETM+, and OLI Combined)        

  • This collection includes images from Landsat 8 OLI,            Landsat 7 ETM+, Landsat 7 ETM+ SLC-off, Landsat 4 and 5            TM, and Landsat 4 and 5 MSS - all the Landsat sensors that utilize            World Reference System-2 (WRS-2).  The scenes are merged together            in chronological order to enable easy browsing through the various            sensors. Scenes from any of the sensors can be searched, previewed,            and ordered from a single scene list.        
  • When an image is selected, it is outlined by a color that is unique            to each sensor.            

    Dataset	Color
    Landsat OLI	Orange
    Landsat ETM+ SLC-off	Green
    Landsat ETM+	Blue
    Landsat TM	Yellow
    Landsat 4 - 5 MSS	Red

  • Because of the large quantity of scenes for the combined datasets,            loading the inventory will be very time consuming when using dialup            internet or other slow connections.        
  • For details on the individual Landsat sensors, please refer to the            specific sensor information above and below.        
  • When scenes are added to the combined sensor scene list, they will            also be added to the scene list for that corresponding sensor.            Conversely, adding scenes to the list for an individual sensor will            be reflected in the combined sensor scene list.  All other scene            list features will be handled in the same way.    

   

• Landsat 7 Enhanced Thematic Mapper Plus        (ETM+)

  • Images acquired from June 1999 - May 2003 are displayed as RGB            composites, bands 5, 4, and 3.        
  • Images are resampled to a pixel size of 240 meters from the             original 30-meter data.        
  • Each Landsat 7 scene is color-stretched based on individual scene            content.  This may result in an apparent mismatch of colors between            scenes.        
  • In the 240-meter display mode, browse images are JPEG compressed            files with an average file size of ~130K. In the 1000-meter display            mode, the browse images are GIFs with an average file size of ~35K.        
  • The browse previews that are used to create the            "Show Browse" display are uncorrected images in satellite            orientation, and they can be viewed in a separate window.     

   

• Landsat 7 Enhanced Thematic        Mapper Plus (ETM+) Scan Line Corrector Off (SLC-Off)

  • Images acquired after July 2003 are displayed as RGB composites,            bands 5, 4, and 3.  Landsat 7 ETM+ scenes acquired from 5/31/03 -            7/14/03 and 9/3/03 - 9/17/03 are not available.        
  • Images are resampled to a pixel size of 180 meters from the             original 30-meter data.        
  • The "Show Browse" option displays an overlay that illustrates the            approximate extent of the SLC-off image gaps.        
  • Each Landsat 7 scene is color-stretched based on individual scene            content.  This may result in an apparent mismatch of colors between            scenes.        
  • In the 240-meter display mode, browse images are JPEG compressed            files with an average file size of ~130K. In the 1000-meter display            mode, the browse images are GIFs with an average file size of ~35K.        
  • The browse previews that are used to create the            "Show Browse" display are uncorrected images in satellite            orientation, and they can be viewed in a separate window.         
  • For more information on SLC-Off data, please see the                         Landsat FAQ.    

   

• Landsat 8 Operational Land Imager (OLI)        

  • Images are displayed as RGB composites, bands 6, 5, and 4.        
  • Images are resampled to a pixel size of 240 meters from the            reduced-resolution LandsatLook "Natural Color" image.        
  • In the 240-meter display mode, browse images are JPEG compressed            files with an average file size of ~130K. In the 1000-meter display            mode, the browse images are GIFs with an average file size of ~35K.        
  • The image displayed in the "Show Browse" window is a            reduced-resolution LandsatLook "Natural Color" image            generated from the full-resolution LandsatLook "Natural Color"            image by scaling the width to 1024 and the height to preserve            the original aspect ratio.    

   

• Landsat 8 Operational Land Imager (OLI) Pre-WRS-2

  • Images acquired by the Landsat 8 satellite prior to achieving            operational (WRS-2) orbit (prior to April 11, 2013).            The geometry of these scenes are not consistent, nor will they            align with data collected April 11, 2013 and beyond.    

   

• MODIS

  • The images are displayed as a 1,4,3 (RGB).         
  • The images generally cover a 10° x 10° area.        
  • Pixels are subsampled to a resolution of approximately 10             kilometers from the original 5 kilometer data.         
  • Each scene is color-stretched based on individual scene content.             This may result in an apparent mismatch of colors between scenes.         
  • The 10 kilometer display browse images are jpgs with an average            file size of 5K. The 5 kilometer browse images are JPEG            compressed with an average file size of 30K.        
  • The "Show Browse" display, which uses a            separate browser window, displays the same 5-kilometer images             shown in the applet.  The exceptions are datasets that have             an annotation on the bottom of the browse.  These browse images             will cover more area than what is shown in the applet.        
  • The browse are displayed in the sinusoidal projection.    

   

• MRLC 2001 Terrain Corrected (TC) and         2001 Reflectance Adjusted (RA)

  • The images are Landsat 7 ETM+ and Landsat 4-5 TM images and do not             show the final MRLC product. They display as a 5,4,3 (RGB)             composite.        
  • Pixels are subsampled to a resolution of 240 meters from the             original 30 meter data.        
  • Each landsat 7 scene is color-stretched based on individual scene            content. This may result in an apparent mismatch of colors between            scenes.        
  • In the 240 meter display mode, browse images            are JPEG compressed with            an average file size of ~130K. For the 1000 meter display mode, the            browse images are GIFs with an average file size of ~35K.        
  • The "Show Browse" images (viewed in a separate browser window) are            raw browse in satellite orientation.        
  • Full-resolution MRLC 2001 Terrain Corrected data may be downloaded            at no charge.    

   

• National Aerial Photography Program (NAPP)

  • NAPP browse images are created from medium resolution digital            products that are captured by a digital camera.  The browse files            are resampled to 72 dpi.        
  • NAPP scenes cover approximately a 5.5 x 5.5 mile area.        
  • NAPP browse on GloVis have been clipped to remove the excess film            margins and the images have been oriented "north up".        
  • Some browse may contain the Moiré pattern artifact.        
    • The Moiré pattern artifact is a pattern in areas where                the spatial frequency of the land area is higher than detector                density on the focal plane in the digital camera used to                capture the image.  The artifact that results is a type of                aliasing known as moiré patterns or moiré waves.                This well-known artifact is not an error in the original film                or the digitizing process. The moiré pattern shown in                some of the browse is not present when scanned at                high-resolution on photogrammetric quality scanners used at the                Earth Resources Observation and Science Center (EROS). For more                information on this artifact, check these web sites:                 http://www.dpreview.com/glossary/digital-imaging/moire                 http://www.maxim-ic.com/appnotes.cfm/appnote_number/928        

   

• North American Landscape Characterization (NALC)    

  • The browse images are Landsat 4 and 5 MSS browse images displayed            as RGB composites, bands 4, 2, 1, with a 2% linear stretch.        
  • Images are resampled to a pixel size of 480 meters from the original            nominal 60-meter data.        
  • In the 480-meter display mode, browse images are JPEG compressed             files with an average file size of ~50K. For the 1000-meter display            mode, the browse images are GIFs with an average file size of ~35K.        
  • The registration of the images in GloVis is inaccurate, however the            original data registration is accurate.        
  • Full-resolution data may be downloaded at no charge.        
  • North American Landscape Characterization (NALC) data consists of            Landsat Multi-Spectral Scanner (MSS) time-series triplicates that            were acquired in 1973, 1986, and 1991 (+/- one year).    

   

• National High Altitude Photography (NHAP)

  • NHAP browse images are created from medium resolution digital            products that are captured by a digital camera.  The browse files            are resampled to 72 dpi.        
  • NHAP scenes for Color Infrared (CIR) cover approximately an 8 x 8            mile area and Black and White (B/W) cover approximately an 11 x 11            mile area.        
  • NHAP browse on GloVis have been clipped to remove the excess film            margins and the images have been oriented "north up".        
  • Some browse may contain the Moiré pattern artifact.        
    • The Moiré pattern artifact is a pattern in areas where                the spatial frequency of the land area is higher than detector                density on the focal plane in the digital camera used to                capture the image.  The artifact that results is a type of                aliasing known as moiré patterns or moiré waves.                This well-known artifact is not an error in the original film                or the digitizing process. The moiré pattern shown in                some of the browse is not present when scanned at                high-resolution on photogrammetric quality scanners used at the                Earth Resources Observation and Science Center (EROS). For more                information on this artifact, check these web sites:                 http://www.dpreview.com/glossary/digital-imaging/moire                 http://www.maxim-ic.com/appnotes.cfm/appnote_number/928        

   

• Systematic ETM+

  • The Level 1G (L1G) data product provides systematic radiometric            and geometric accuracy, which is derived from data collected            by the sensor and spacecraft.        
  • The "Show Browse" images (viewed in a separate browser window)            were rotated, aligned, and georeferenced to UTM map projection.        
  • Geometric accuracy of the systematically corrected product should            be within 250 meters (1 sigma) for low-relief areas at sea level.        
  • These were used as input to the Tri-Decadal data set so they only            cover the time period from June 29, 1999 to May 31, 2003.    

   

• TerraLook

  • The TerraLook product is a user-selectable collection of simulated            natural-color, JPEG-compressed satellite images. The TerraLook            collection consists of georegistered Advanced Spaceborne Thermal            Emission and Reflection Radiometer (ASTER) images and Global            Land Survey (GLS) images from five epochs (circa 1975,            1990, 2000, 2005, and 2010).            The TerraLook product is delivered  as a single zip file using ftp.        
  • The same browse images are used for the TerraLook product and for            the Aster and GLS products. See the descriptions of the             ASTER and GLS            browse images for more information.        
  • The browse images use different band combinations and stretches            than are used in the TerraLook product. As a consequence, the            browse images will not look the same as the TerraLook product.        
  • For more information on TerraLook, go to                         http://terralook.cr.usgs.gov.    

   

• Tri-Decadal ETM+ (1999-2003)

  • The Tri-Decadal Global Landsat Orthorectified (previously Landsat            Orthorectified) ETM+ browse images are displayed as a 5,4,3 (RGB)            color composite.        
  • Pixels are subsampled to a resolution of 240 meters from the            original 30-meter data.        
  • Each Landsat 7 scene is color-stretched based on individual            scene content. This may result in an apparent mismatch of colors            between scenes.        
  • In the 240 meter display mode, browse images are JPEG compressed            with an average file size of 147K. For the 1000 meter display mode,            the browse images are GIFs with an average file size of 8K.        
  • The "Show Browse" images (viewed in a separate browser window)            are raw browse in satellite orientation.        
  • Full-resolution data may be downloaded at no charge.    

   

• Tri-Decadal ETM+ Pan (1999-2003)

  • The Tri-Decadal Global Landsat Orthorectified (previously Landsat            Orthorectified) ETM+ Pan browse images are displayed as a 7,4,2            (RGB) color composite.        
  • Pixels are subsampled to a resolution of 240 meters from the            original 30-meter data.        
  • Each Landsat 7 scene is color-stretched based on individual            scene content. This may result in an apparent mismatch of colors            between scenes.        
  • In the 240 meter display mode, browse images are JPEG compressed            with an average file size of 147K. For the 1000 meter display mode,            the browse images are GIFs with an average file size of 8K.        
  • The "Show Browse" images (viewed in a separate browser window)            are raw browse in satellite orientation.        
  • Full-resolution data may be downloaded at no charge.    

   

• Tri-Decadal ETM+ Pan Mosaics

  • The Tri-Decadal Global Landsat Orthorectified ETM+ Pan Mosaic            browse images are displayed as a 7,4,2 (RGB) color composite.        
  • Pixels are subsampled to a resolution of 285 meters from the            original 30-meter data.        
  • The mosaics cover a 5 degree (north-south) segment of a standard 6            degree wide (east-west) UTM zone.  It is further subdivided into            four 2.5 degree by 3 degree quadrants.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.    

   

• Tri-Decadal TM (1987-1997)

  • The Tri-Decadal Global Landsat Orthorectified (previously Landsat            Orthorectified) TM browse images are displayed as a 7,4,2 (RGB)            color composite.        
  • Pixels are subsampled to a resolution of 480 meters from the            original 30-meter data.        
  • In the 480 meter display mode, browse images are JPEG compressed            with an average file size of 38K. For the 1000 meter display mode,            the browse images are GIFs with an average file size of 23K.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.    

   

• Tri-Decadal TM Mosaics

  • The Tri-Decadal Global Landsat Orthorectified TM Mosaic browse            images are displayed as a 7,4,2 (RGB) color composite.        
  • Pixels are subsampled to a resolution of 700 meters from the            original 30-meter data.        
  • The mosaics cover a 5 degree (north-south) segment of a standard 6            degree wide (east-west) UTM zone.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.    

   

• Tri-Decadal MSS 4-5 (1982-1987)

  • The Tri-Decadal Global Landsat Orthorectified (previously Landsat            Orthorectified) MSS 4-5 browse images are displayed as a 4,2,1            (RGB) color composite.        
  • Landsats 4-5 MSS data has sparse coverage and used only to fill in            gaps in coverage for the Tri-Decadal MSS 1-3 dataset.        
  • Pixels are subsampled to a resolution of 480 meters from the            original 80-meter data.        
  • In the 480 meter display mode, browse images are JPEG compressed            with an average file size of 38K. For the 1000 meter display mode,            the browse images are GIFs with an average file size of 23K.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.    

   

• Tri-Decadal MSS 1-3 (1972-1983)

  • The Tri-Decadal Global Landsat Orthorectified (previously Landsat            Orthorectified) MSS 1-3 browse images are displayed as a 7,5,4            (RGB) color composite.        
  • Landsats 1-3 MSS data provide worldwide historical coverage.        
  • Pixels are subsampled to a resolution of 480 meters from the            original 80-meter data.        
  • In the 480 meter display mode, browse images are JPEG compressed            with an average file size of 38K. For the 1000 meter display mode,            the browse images are GIFs with an average file size of 23K.        
  • The "Show Browse" images (viewed in a separate browser window)            were generated from full-resolution data that is orthorectified            and UTM-projected, using the World Geodetic System 1984 datum.        
  • Full-resolution data may be downloaded at no charge.    

NOTE: Because the browse images for some datasets are processed from raw or Level 0 uncorrected data, the positional accuracy of the scenes can only be expected to be accurate within a few pixels. These browse images are not intended for analytical use, but only as a visual scene selection aid.

Back to the Table of Contents

Frequently Asked Questions (FAQs)

Q: How is the cloud cover calculated,    and why are some scenes cloudy when the cloud cover is reported    to be 0%?

A: The cloud cover index is an automated calculation which may    provide a useful estimate, but the algorithm is not always accurate when it    encounters snow, ice, water, or other unusual scene content. Haze, thin    clouds, and small clouds ("popcorn") can frequently be missed in the cloud    cover assessment.  

Q: Why are some Landsat scenes    "missing"?

A: GloVis displays most of the Landsat scenes, but some are not    available through this tool. Please refer to the     Landsat    FAQ for details on searching for and ordering Landsat scenes.

Q: Can I find the actual    gain and bias values for a Landsat scene on GloVis?

A: No, you will not find the actual gain and bias values on GloVis.    Gain and bias values can only be obtained when actual data is ordered    because to gain and bias values are only available in the final product    metadata.  These coefficients can then be applied with the DN values within    the imagery to convert to accurate radiance values.

    For information on gain and bias values, please refer to the     Landsat    FAQ.

Q: Where can I find out more about    Landsat MSS, TM, ETM+, and OLI data?

A: Please refer to the     Landsat    FAQ for information about all of the Landsat missions.

Q: Does red in ASTER images always represent vegetation?

A: Red colors in the VNIR images generally represent vegetation.

Q: Why do some ASTER images have a    ‘smeared‘ line in them?

A: Images with smeared lines generally indicate a temporary     detector-related problem during the course of acquisition. They are     infrequent and irreversible. They generally result in a data gap on the     image. Depending on the amount of area affected and your application needs,    you may want to find an alternative scene.

Q: Why are some ASTER images    completely white?

A: Completely white, or nearly completely white, browse images    exist because saturated cloud cover leaves little to no useful image data.

Q: Why are some ASTER L1A images    missing?

A: If you are unable to find ASTER L1A images in GloVis,    please try Reverb (http://reverb.echo.nasa.gov/reverb).

Q: Why does the EO-1 Scene ID list a    path and row that is different than the path and row of the center part    of the image?

A: EO-1 imagery is collected based on a targeted center point. The    path and row listed in the Scene ID represents when the EO-1 instruments     began imaging, even though the target point may fall in the next row. In     the diagram below, the coordinates for Target 2 fall within the WRS row    below that of the coordinates for Target 1. However, since the instruments    began imaging Target 1 and Target 2 in the same path/row, both images would    have the same Target WRS path and Target WRS row in the     Scene ID.  EO-1 is not able to image both targets on the same date;    therefore, the difference in the Scene IDs would show up in the Julian day     of acquisition.    

Q: If NAPP scenes cover a square area,    why do they appear rectangular in GloVis?

A: NAPP browse images are provided in a geographic projection with    pixels that are not square in geographic coordinates.  To be properly    displayed in GloVis, the browse images are resized to make the pixels    square in geographic coordinates.  The result is that the browse images    end up being rectangular.

 

Q: When I download a NALC    dataset, will I receive all of the images for that triplicate?

A: Yes, all of the images available in the NALC triplicate will be    included in the downloaded product, even though only a    single browse image is displayed in GloVis.

影像介绍

原文：http://www.cnblogs.com/lovebay/p/5080840.html