Getting Started with MODIS Version 6 Vegetation Indices Data Part 2
This video focuses on the National Aeronautics and Space Administration’s (NASA) Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Version 6 Vegetation Indices data distributed by NASA’s Land Processes Distributed Active Archive Center (LP DAAC). Information about MODIS Vegetation Indices quality information, including how to decode quality bits, tools for working with quality data, and where to find additional information, will be provided. To learn more about MODIS Version 6 Vegetation Indices 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 Systems (EROS) Center in Sioux Falls, South Dakota. The LP DAAC ingests, archives, processes and distributes NASA Earth science land processes data and information.
Location Taken: Sioux Falls, SD, US
Video Credits: Content created by Danielle Golon (Contractor to USGS EROS)
Getting Started with MODIS Version 6 Vegetation Indices 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 MODIS Version 6 Vegetation Indices Data” video series. This video will cover the Science Datasets or SDSs in each MODIS Vegetation Indices file, the fill values and scale factor for the data and how to apply it, how to visualize Vegetation Indices using a color map, and how to find Vegetation Indices resources on the LP DAAC website. The MODIS Vegetation Indices Version 6 products provide consistent information about the greenness of vegetation on the Earth’s land surface. This data product family provides two types of vegetation indices, the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI). NDVI is calculated using a ratio of the Red and Near Infrared or NIR wavelengths, whereas EVI is calculated using a ratio of the Red, NIR, and Blue wavelengths along with other factors. In the NDVI healthy vegetation is shown as it absorbs the visible light and reflects more of the near-infrared light whereas unhealthy vegetation reflects more of the visible light and less of the near-infrared light. The EVI layer is similar to NDVI but it also reduces atmospheric influences and accounts for bare soil interference. MODIS vegetation indices are measured between -1 and 1. NDVI values less than 0.3 and EVI values less than 0.2 generally indicate a lack of green vegetation, or barren areas. Higher vegetation indices values indicate areas of dense green vegetation, such as fully developed forest or crop canopies. MODIS Vegetation Indices products are distributed as Hierarchical Data Format – or HDF files and the file name contains “MOD13” indicating Terra MODIS observations or “MYD13” for Aqua MODIS observations. Here is a visual representation of the data stored within a single Terra MODIS Version 6 Monthly Vegetation Indices 1 kilometer Level 3 gridded product, MOD13A3, HDF file. The HDF file for this product contains NDVI and EVI data, quality information, four reflectance bands, information about angles of the sun and satellite, and the day of the year. It is important to know that a scale factor must be applied to the NDVI and EVI data values before you begin using the data. To learn more about the specific scale factors, fill values, and valid ranges for the various MODIS Version 6 Vegetation Indices 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. Here is an example of an NDVI image of central Mexico from August 12th to 27th, 2016, shown using the Terra MODIS Version 6 16-day Vegetation Indices 250 meter level 3 tiled in sinusoidal grid projection product, MOD13Q1. NDVI are available as a single science dataset. A colormap can be used to better visualize variations in the presence of vegetation. A colormap is an RGB assignment of colors to certain values. A colormap can be added using most Geographic Information System or GIS software. Here is the same NDVI image shown using a colormap. On this colormap 0.0001 to 0.3 is a color ramp ranging from light brown to dark brown. A light to dark green color ramp is used for values from 0.3001 to 1.0. Fill values are classified as blue. For examples of how MODIS Vegetation Indices products can be used in scientific applications, visit the LP DAAC website. The Publications table has relevant literature, the Data in Action section has short stories about scientific applications, and the E-Learning page has tutorials, presentations, and other product resources. Thank you for watching this video. For more information on MODIS Version 6 Vegetation Indices data please visit the LP DAAC website at lpdaac.usgs.gov.