An Introduction to MODIS Version 6 Data.
Presented by the Land Processes Distributed Active
Archive Center (LP DAAC). The Moderate Resolution Imaging
Spectroradiometer, or MODIS
instrument operates on both NASA’s Terra and Aqua spacecraft.
The orbit of each spacecraft allow MODIS to capture the
entire Earth every one to two days, providing data products
with spatial resolution ranging from 250 to 5,600 meters.
The LP DAAC currently distributes more than 100
MODIS Version 6 products covering Surface Reflectance,
Temperature, and more. This video will cover how to
learn more about MODIS Version 6 data using the
LP DAAC website, the MODIS File Naming Convention,
and the external metadata. One of the first places to
learn more about MODIS Version 6 data is the LP DAAC’s
website, lpdaac.usgs.gov. In-depth information about
MODIS Version 6 data can be found under the “Dataset
Discovery” tab. Hover over “Dataset Discovery”, then
hover over “MODIS” and click on the “MODIS Products Table”.
The “MODIS Products Table” lists all of the MODIS products
distributed by NASA’s LP DAAC. Click on the “Version 6” tab
to see the MODIS Version 6 products. The table provides
information on the product short name, the dataset,
the product, the pixel size, and the temporal granularity.
The searchable table allows users to search for specific
data products in the MODIS product table. For example,
type in “leaf” to bring up Leaf Area Index data from
the Terra satellite (MOD), the Aqua satellite (MYD),
and data that are combined from both satellites (MCD).
Type in the specific short name of a product to find
that product. For example, type in MOD09A1. Clicking on
the hyperlinked name leads to more product information.
All of the MODIS Version 6 Digital Object Identifier
(DOI) Landing Pages have the same layout. At the top of
the DOI Landing Page is the product short name and the
product long name. The “Description” section
contains a brief description of the product, as well as
any improvements or changes since the previous version
of the product. The description section also
contains the necessary information for properly
citing the data product and a citation generator.
To the right of the description section is a
visual example of the product tile, a brief
informational outline about the product, and the tools
that can be used to access the data. The next section of
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 (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
(ATBD) which provides descriptions of the algorithms
and calculations that are fundamental to the product.
The fourth section lists the data tools that provide users
with access to download and explore the data product.
This section also contains data service tools that allow
users to manipulate data before downloading any files.
Some of these services include reprojection,
subsetting the data layers, and downloading data in a
different file format. The final section provides
resources from the E-Learning page. 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
“AppEEARS” in the search bar to bring up the E-Learning
resources that relate to the product and AppEEARS. In this
case, the resources include a video about accessing MODIS
data with AppEEARS and a python tutorial on using
the AppEEARS Quality Service to decode MODIS quality
information. Now that the product information on the
LP DAAC website has been explained, information on how
to read the MODIS filename will be discussed. The MODIS
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 MODIS sinusoidal Horizontal-Vertical
tile system. The H/V grid is accessible on the MODIS overview
page on the LP DAAC’s website. The fourth part indicates the
product version. The fifth part indicates the Julian date of
production including the year, day, hours, minutes, and seconds.
The last part is the file format. MODIS Version 6 are provided as
an HDF file. Another great place to find information about the
data is the external metadata file in XML format. The XML
file is available through any data access client used to
download MODIS Version 6 data. The metadata is data about
the data. It provides useful information about a specific
granule. The metadata includes the data product DOI link,
which is needed to properly cite the data. It also provides
information ranging from the granule’s corner coordinate
boundaries to the input granules for multiday products.
Thank you for watching our video. To learn more about
MODIS Version 6 please visit our website at lpdaac.usgs.gov.