An Introduction to Suomi-NPP NASA VIIRS Data.
Presented by the Land Processes Distributed Active Archive Center or LP DAAC.
This video will provide information on data produced by NASA from the VIIRS instrument aboard
the Suomi-NPP satellite.
An overview of the Suomi-NPP VIIRS mission will be provided as well as how to
find out more from the LP DAAC website, how to understand the VIIRS File Naming
Convention, and how to use the external metadata file.
The VIIRS instrument operates on the Suomi-NPP spacecraft, which is a joint mission between NOAA and NASA.
The VIIRS satellite sensor provides a continuation of the Terra and Aqua Moderate Resolution Imaging
Spectroradiometer or MODIS missions.
VIIRS was launched on October 28, 2011 and orbits 824 kilometers or 512 miles above
the Earth’s surface.
At this elevation, the VIIRS swath width is 710 kilometers greater than MODIS’ and has
less gaps in coverage near the equator than MODIS.
The orbit of this spacecraft allows VIIRS to capture the entire Earth every day providing
data products at two spatial resolutions, 375 and 750 meters, which are then resampled to
500 meters, 1 kilometer, and 0.05
degrees to promote consistency with the MODIS data products collection.
The LP DAAC distributes land discipline-related NASA VIIRS data products.
One of the first places to learn more about Suomi-NPP NASA VIIRS data is the
LP DAAC’s website: lpdaac.usgs.gov.
In-depth information about Suomi-NPP NASA VIIRS data can be found under the Dataset Discovery tab.
Hover over Dataset Discovery, then hover over VIIRS and click on the VIIRS Products Table.
The VIIRS Products Table lists all of the Suomi-NPP NASA VIIRS Products distributed by NASA’s LP DAAC.
The table provides information on the product short name, the dataset, the pixel size, the
product, and the temporal granularity.
Clicking on the hyperlinked name leads to more product information.
Each VIIRS data product has a Digital Object Identifier or DOI, and with that a
webpage that provides important information.
Each page has the same layout.
At the top of the DOI Landing Page is the data product short name and long name.
The Description section contains a brief description of the product.
The description section also contains the necessary information for properly citing the data product, including
the DOI, and a Citation Generator.
To the right of the description section is a visual sample example from the product,
a brief informational outline about the product, and the tools that can be used to
access the data.
The next section on the DOI Landing Page describes Characteristics of the data, including high
level information about the Collection - or product family - and the granules in the collection.
Below that is information about each of the Data Layers contained in the Hierarchical Data
Format or HDF file.
This section also provides links to information about the Product Quality, which looks at quality
control aspects of each pixel in the product, and any Known Issues with the data.
The third section provides links to Documentation that relates to that specific data product.
These documentation sources include the User Guide, which provides a more in-depth and up-to-date explanation
of the product, and the Algorithm Theoretical Basis Document or ATBD which provides descriptions of
the algorithms and calculations that are fundamental to the product.
The fourth section lists the tools that provide users with the ability to download and
explore the data product.
This section also contains information about services that enable users to reproject, subset, and download
data in a different file format.
The final section provides E-learning resources from the LP DAAC.
These resources include tutorials, use cases, scripts, videos, and past webinars and presentations that relate
to the data product.
The E-learning table is searchable.
For example, type Python in the search bar to bring up the E-learning resources that
relate to the product and Python.
In this case, the resource is a Webinar and Presentation on using R and Python
with land remote sensing data.
Now that the product information on the LP DAAC website has been explained, information on
how to read the VIIRS filename will be discussed.
The VIIRS filename itself can tell users a lot about the granule without needing to preview it.
Here is an example of a granule ID.
The first part of the Granule ID is the product short name.
The second part indicates the Julian date of acquisition.
The third part indicates the location of the granule based on the VIIRS Sinusoidal Tile
System, which is the same as the MODIS sinusoidal Horizontal-Vertical H/V tile system.
The fourth part indicates the product version.
The fifth part indicates the Julian date of production including the year, day, hours, minutes,
and seconds in UTC.
The last part is the file extension.
VIIRS data are provided in the HDF-EOS5 file format.
Another great place to find information about the data is the external metadata file which
is provided in XML format.
The XML file is available through any data access client used to download Suomi-NPP NASA VIIRS data.
Metadata is data about data.
Granule-level metadata provides useful information about each specific data file.
This metadata file includes the data product DOI link, which is needed to properly cite the data.
It also provides additional information like the granules corner coordinate boundaries.
Thank you for watching our video.
To learn more about Suomi-NPP NASA VIIRS data products please visit lpdaac.usgs.gov.