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Landsat Missions

LandsatLook Images

LandsatLook images are full resolution files that are included as options when downloading Landsat data from EarthExplorer (http://earthexplorer.usgs.gov), GloVis (http://glovis.usgs.gov) or the LandsatLook Viewer (http://landsatlook.usgs.gov).

Derived from Landsat Level 1 data products, these images are useful for image selection and for visual interpretation. Algorithms applied to the images will cause minor local smoothing to the data values of the images, and while this should not affect interpretation of the images, it is not recommended that they be used in digital analysis.

LandsatLook products

These LandsatLook products are available to download:

  1. LandsatLook "Natural Color" Image: a composite using three bands to show a 'natural' looking image.
    • Bands 6,5,4 are used for Landsat 8 OLI images
    • Bands 5,4,3 are used for Landsat ETM+ and TM images
    • Bands 2,4,1 are used for Landsat MSS images
  2. LandsatLook "Thermal" Image: a one-band gray scale image to display thermal properties.
    • Band 10 (Landsat 8 TIRS), Band 61-high gain (ETM+), and Band 6 (TM) are used
    • Not available for MSS scenes
  3. LandsatLook Images with Geographic Reference: a 'bundle' that includes both the natural color and thermal .jpg images along with geographic reference files to import into a geographic information system or image processing software packages
    • Uses Geospatial Data Abstraction Library Extensible Markup Language files (GDAL XML) and ESRI World Files*
    • In some software packages, it will be necessary to import the .wld and .xml files separately to successfully create a georeferenced image.
  4. The Landsat 8 Geographic Reference bundle also includes the 8-bit quality band (.png) generated from the 16-bit quality band. The 8-bit quality band includes values representing bit-packed combinations of surface, atmosphere, and sensor conditions that can affect the overall usefulness of a given pixel.

    The table below gives the bits and colors associated with the 8-bit quality band:

    8-Bit LandsatLook QA Band - Read bits from RIGHT to LEFT <- starting with Bit 0
    Bit 7 6 5 4 3 2 1 0
    Description Cloud* Cirrus* Snow/Ice* Vegetation* Water* Terrain Occlusion Dropped Frame Designated Fill
                     
    *Set for highest confidence value (11)
  5. LandsatLook “Quality” Image (Landsat 8 only): 8-bit quality band file (.png) that includes pixel color mapping assignments, as shown in the table above. The bit assignments shown in this table do not apply to the LandsatLook Quality Image file, so this file should be used for display purposes only. (Note that pixels without a color assignment are transparent and will show up as background color in photo viewer applications. To view the .png correctly, you must change your photo viewer background to a color not shown in the table above.)

*GDAL XML and ESRI referencing systems demonstrate high standards. ESRI world files are simple and widely supported, but do not include projection information. GDAL XML files are less well supported, but contain important projection information.

LandsatLook “Natural Color” Image: Landsat 8 Path 45 Row 30 Acquired April 23, 2013
Figure 1. LandsatLook “Natural Color” Image: Landsat 8 Path 45 Row 30 Acquired April 23, 2013
LandsatLook “Thermal” Image of Landsat 8 Path 45 Row 30 Acquired April 23, 2013
Figure 2. LandsatLook “Thermal” Image of Landsat 8 Path 45 Row 30 Acquired April 23, 2013
LandsatLook “Quality” Image of Landsat 8 Path 45 Row 30 Acquired April 23, 2013
Figure 3. LandsatLook “Quality” Image of Landsat 8 Path 45 Row 30 Acquired April 23, 2013 with photo viewer background color set to dark grey.

Additional Information about LandsatLook images

About .jpeg images: Most geographic information systems and image processing software packages easily support .jpeg images. To create the .jpeg images, the Landsat data is mapped to a 1-255 range, with the fill area set to zero. If a no-data value is set to zero, the compression algorithm may introduce zero-value artifacts into the data area causing very dark data values to be displayed as no-data. Other image formats support a layer that explicitly defines the mask area. (Two examples are PNG and JPEG2000. The PNG algorithm creates much larger images. The JPEG2000 algorithm is not as widely supported.)

Top of Atmosphere (TOA): Reflectance values were calculated from the calibrated scaled DN image data. The reflectance values were scaled to a 1-255 range using a gamma stretch with a gamma=2.0. This stretch was designed to emphasize vegetation without clipping the extreme values.

Thermal band Units: Image brightness temperature values were calculated from the calibrated scaled DN image data. An image specific 2% clip and a linear stretch to 1-255 were applied to the brightness temperature values.





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Page Last Modified: 04/24/14 01:23 pm
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