Getting Started with VIIRS Surface Reflectance Data Part 1

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Getting Started with VIIRS Surface Reflectance Data Part 1: All About Accessing Data
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This video focuses on Visible Infrared Imaging Radiometer Suite (VIIRS) surface reflectance data products created by National Aeronautics and Space Administration (NASA) and distributed by the Land Processes Distributed Active Archive Center (LP DAAC). 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. Information about characteristics of the S-NPP VIIRS satellite sensor and the NASA VIIRS Surface Reflectance data products, as well as how to access the data using NASA’s Earthdata Search is provided. To learn more about NASA 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

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Length: 00:08:33

Location Taken: Sioux Falls, SD, US

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Getting Started with NASA’s Visible Infrared Imaging Radiometer Suite or VIIRS Surface Reflectance Data Part 1: All About Accessing Data. Presented by the Land Processes Distributed Active Archive Center or LP DAAC. This video is part 1 of the “Getting Started with NASA’s VIIRS Surface Reflectance Data” video series. This video will provide information about the NASA VIIRS satellite sensor, the NASA VIIRS Surface Reflectance data products and how to search for and download these data using NASA’s Earthdata Search Client data access tool. The VIIRS satellite sensor is one of five instruments on-board the Suomi National Polar-orbiting Partnership (S-NPP) satellite. S-NPP was launched on October 28, 2011 and is the first in a series of four Joint Polar Satellite System (JPSS) satellites. VIIRS is part of a collaborative mission between the National Oceanic and Atmospheric Administration (NOAA) and NASA. NASA is applying algorithms similar to the algorithms used in Moderate Resolution Imaging Spectroradiometer (MODIS) data to the NASA VIIRS data. NASA VIIRS data are considered a continuation of the MODIS data, just as MODIS data are a continuation of Advanced Very High Resolution Radiometer (AVHRR) data. VIIRS observes the entire Earth’s surface twice each day from a polar orbit at 824 kilometers or 512 miles above the Earth’s surface. The 3,000 kilometers swath width of the VIIRS instrument, which is 710 kilometers greater than that of MODIS, allows for no gaps in coverage, similar to those observed in MODIS near the equator. The VIIRS instrument provides 22 spectral bands at two spatial resolutions, 375 meters and 750 meters, which are resampled to 500 meters, 1 kilometer, and 5,600 meters in the NASA produced data products to promote consistency with the MODIS heritage. The LP DAAC distributes four different types of VIIRS Surface Reflectance products. These include two Daily VIIRS Surface Reflectance products and two 8-Day Surface Reflectance products. All data distributed by the LP DAAC are available for download at no charge. VIIRS data are distributed as Hierarchical Data Format – Earth Observing System 5 or HDF-EOS5 products. The VIIRS Surface Reflectance products are level 3 products, meaning they have been atmospherically corrected, gridded into a map projection, and temporally composited. The daily Surface Reflectance products are available as a 0.05 degree or 5,600 meter Global Climate Modeling Grid or CMG and as a 1 kilometer or 500 meter tiled product in sinusoidal projection, based on the MODIS sphere. The 8-day Surface Reflectance products are available as 1 kilometer and 500 meter tiled products also in sinusoidal projection. Data products are available from January 19, 2012 to present. Detailed information about each of the individual products can be found on the LP DAAC website at lpdaac.usgs.gov. The surface reflectance data are created by adjusting top-of-atmosphere reflectance to compensate for atmospheric effects. Corrections are made for the effects of molecular gases, including ozone and water vapor, and for the effects of atmospheric aerosols. The VIIRS Surface Reflectance products contain two different types of Surface Reflectance Bands. The M indicates bands with a nadir resolution of 750 meters, which are resampled to 1 kilometer. The I indicates bands with a nadir resolution of 375 meters, resampled to 500 meters. The M bands are only in the VIIRS surface reflectance products that provide 1 kilometer spatial resolution, including the 8-Day VNP09A1 product and the Daily VPN09GA product. Likewise, the I bands are only in the VIIRS surface reflectance products that provide a 500 meter spatial resolution, including the 8-Day VNP09H1 product and the Daily VNP09GA product. The Daily Climate Modeling Grid VNP09CMG product contains both the I and M bands but at a 0.05 degree or approximately 5,600 meter spatial resolution. The VIIRS Surface Reflectance products contain bands that are in a spectral range that is similar to the MODIS Surface Reflectance bands, but not exact. The LP DAAC website also offers several ways to download VIIRS Surface Reflectance data products. At the bottom of the DOI Landing Page for each product are links to useful data access tools. In this video, downloading data using NASA’s Earthdata Search Client data access tool will be demonstrated step-by-step. The Earthdata Search home page can also be accessed from the Tools section of the LP DAAC website. From the Earthdata Search home page, search.earthdata.nasa.gov, click on the “Earthdata Login” button to login with your NASA Earthdata account. If you do not have an Earthdata account, click on the register button and follow the prompt to create one. Now, search for the VIIRS Daily Surface Reflectance 1 kilometer and 500 meter level 3 gridded product, VNP09GA. Type “VNP09GA” in the search bar and hit enter. Click on the VNP09GA data product. This will pull up all of the VNP09GA granules. Parameters for a specific time and location can be set above the map. For this video let’s look at the Daily Surface reflectance for the United States City of Portland, Oregon during the summer of 2012. First, pan and zoom the map to Portland. Change the temporal range by clicking on the temporal icon and then click on the Start date and change the date to “June 20, 2012.” Now, change the End date to “September 21, 2012” and click on apply filter. To change the spatial information, click on the spatial icon and select “rectangle” from the drop down menu. Draw a rectangle around Portland. You will now see green outlines that indicate the footprint of the VIIRS tiles contained in your rectangle. The granules from 2012 that are located in the selected area are now listed in the white box at the bottom of the page. Above the granule list are options to “Download Data” which allows a user to download all of the matching granules, an “i” icon to learn more about the data collection, a filter icon to further filter the data, and a plus sign icon, which allows a user to add multiple data products to their Earthdata Search project. Click on the first box containing a scene in the bottom white box to select the most recent scene. This box contains a preview of the granule, the VIIRS filename, the dates of the data, an “x” in the upper right hand corner to remove the scene from your granule list, an “i” for more information, and the retrieval icon to download a single granule. Click on the “i” icon to bring up the metadata for the selected granule. Remember, metadata are data about data. The metadata include the DOI, which is necessary for proper citation, as well as information on the scene’s corner coordinates, input granules, and more. Click on the “Metadata” tab for links to download metadata in different standard formats. Click on “Back to Granules” to return to the granule list. Click on “Download Data” to download all of the granules in the granule list. Now, review the data download order on the “Data Access” page, this page lists the number of granules in the order and the size of the order. From here users can select the service options. Select “Direct Download” to instantly receive the granules in the order or select “Stage for Delivery” to receive the granules via email. Click on “submit” or “continue” and then “submit” to submit the order. Depending on the data access method, the data can be accessed immediately or will be sent to the user via email. Thank you for watching our video. For more information on NASA’s VIIRS Surface Reflectance data please visit the LP DAAC website at lpdaac.usgs.gov