Getting Started with VIIRS Surface Reflectance Data Part 2

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Getting Started with VIIRS Surface Reflectance Data Part 2: Using the Data
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This video focuses on how to use Visible Infrared Imaging Radiometer Suite (VIIRS) Surface Reflectance data products created by the National Aeronautics and Space Administration (NASA). VIIRS is a sensor that flies on the Suomi National Polar-orbiting Partnership (S-NPP) satellite, which was launched as a partnership between the National Oceanic and Atmospheric Administration’s (NOAA) and NASA. NASA VIIRS Surface Reflectance data products are distributed by NASA’s Land Processes Distributed Active Archive Center (LP DAAC). Information about the definition of “Surface Reflectance”, the types of NASA VIIRS Surface Reflectance data products, and how to apply a scale factor when preparing the data for use will be provided in this video. The video will also explore various surface reflectance band combinations that are beneficial for a variety of science applications as well as where to find resources about processing NASA VIIRS surface reflectance data on the LP DAAC’s website. To learn more about on VIIRS Surface Reflectance data and other data products distributed by the LP DAAC please visit https://lpdaac.usgs.gov/.

The LP DAAC is one of twelve NASA Earth Observing System Data and Information System (EOSDIS) DAACs. It is located at the United States Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota. The LP DAAC ingests, archives, processes and distributes NASA Earth science land processes data and information. 

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Image Dimensions: 1280 x 720

Date Taken:

Length: 00:04:31

Location Taken: Sioux Falls, SD, US

Transcript

Getting Started with NASA’s Visible Infrared Imaging Radiometer Suite or VIIRS Surface Reflectance Data Part 2: Using the Data. Presented by the Land Processes Distributed Active Archive Center or LP DAAC. This is part 2 of the “Getting Started with NASA VIIRS Surface Reflectance Data” video series. This video will cover what “Surface Reflectance” means, the types of VIIRS Surface Reflectance products distributed by the LP DAAC, the scale factor of the data and other data values, various VIIRS band combinations, and how to find VIIRS Surface Reflectance resources on the LP DAAC website. Surface reflectance can be described as the amount of light reflected by the surface of the Earth. VIIRS surface reflectance data are estimates of surface reflectance in each of the VIIRS reflective bands. Surface reflectance is a unitless ratio of surface radiance to surface irradiance with a value that typically falls between 0.0 and 1.0. VIIRS Surface Reflectance products are distributed as Hierarchical Data Format – Earth Observing System 5 – or HDF-EOS5 files. The file name contains the shortname, “VNP09”. Here is a visual representation of the data stored within a single file for the VIIRS Daily Surface Reflectance Level 3 gridded product, VNP09GA. The file for this product contains information about the satellite, the sun angles, the Surface Reflectance bands, quality information, and information about the satellite observations.  It is important to know that before you begin using the data, a scale factor must be applied to Surface Reflectance data values. For VIIRS Surface Reflectance products a scale factor of 0.0001 should be applied to the Surface Reflectance bands, resulting in data values typically between 0 and 1. Data values that fall outside this range are considered fill values. To learn more about the specific scale factors, fill values, and valid ranges for the various Surface Reflectance product layers, please see the DOI Landing Pages on the LP DAAC’s website at lpdaac.usgs.gov. Once you have an understanding of these values you can work with and observe each of the science datasets. Stacking, or compositing, the surface reflectance bands combines the band wavelengths to emphasize different aspects of the Earth’s surface. Specific bands are assigned to the Red, Green, and Blue portions of the image. Today we will demonstrate three band combinations using the 1 kilometer layers of the VNP09GA product. Band stacking can be done in most types of Geographic Information Systems (GIS) software. The band combination M5-M4-M3 creates a true color image and is a representation of how the human eye would see the area. Here is a view of the Northwestern United States using the M5-M4-M3 band combination. Vegetation is shown as green, the snow and clouds as white, and the barren areas are tan or brown. Another band combination is M3 - M10 - M11, which highlights snow and ice. Here is the same location shown using the M3 -M10 - M11 band combination. In this band combination snow is shown as red, ice in clouds as light pink, clouds are white, water is shown as a dark red, vegetation as green, and deserts are a light blue-green color. A third band combination, M10 – M7 – M5, is used to show Natural Color. This band combination exaggerates natural colors, making it easier to differentiate between land features. In this image vegetation is shown as bright shades of greens, land as shades of brown, clouds and water are shown as shades of blue. For examples of how VIIRS Surface Reflectance products can be used in scientific applications, visit the LP DAAC website. The E-Learning page has tutorials, presentations, and other product resources related to the VIIRS Surface Reflectance data. Stayed tuned for future Data in Action and Publications using VIIRS data! Thank you for watching our video. For more information on VIIRS Surface Reflectance data please visit the LP DAAC website at lpdaac.usgs.gov