Part 4—Select NEO Data and Explore NEO Interface

Step 1 – Select and Display a Map of the NEO Dataset Vegetation Index [NDVI]

Go to the NASA Earth Observations (NEO) homepage . The NEO website will open in a new browser window. Be sure to use a Web browser that is both Flash and Java enabled. NEO organizes datasets into five categories: Ocean, Atmosphere, Energy, Land, and Life.

Step 2 – Access and Learn about Vegetation Index Data

  1. Click the Life tab just below the image. Locate the Vegetation Index (NDVI) dataset in the list and select it.

  2. Once the NDVI image is displayed, click View to be sure you are displaying the correct map for the date you are interested in. In this case the view is of June 1, 2011 to July 1, 2011.

  3. Each of these images represents a "composite" picture that shows the "monthly average" measurements of vegetation index. What does this mean?

    Satellites that go over the poles in their orbits aren't far enough away from Earth to take a picture of the whole planet at one time. Instead, they take measurements of the part of the planet that is directly beneath them on each orbit. Measurements are made along a strip centered on satellites' ground tracks. Scientists take the measurements from all the individual ground tracks or swaths and digitally stitch them together into one composite image. This way, we can see measurements for the whole Earth at once. In this case, measurements taken over an entire month are used to make the image. For locations that the satellite passed over more than once during the month, all the values for each location are averaged.
  4. Notice the color legend below the Vegetation Index image. Examine it and the map to understand what the colors on the map mean.

    • Where in the world do you see the highest values?
    • What areas have the lowest values?
    • What do you know about those areas?
    • Why do you think these areas have high or low values?
  5. To learn more about the Vegetation Index dataset, click the link About this dataset located to the left of the legend.
  6. Note the different levels of information about the dataset. Use the Less Detail | More Detail links or the short, medium, and long page icons to toggle between less complex and more complex explanations.

  7. Find the answers to the following questions within the description.
    • What is NDVI?
    • What is it measure of?
    • Why is it important for scientists and policy makers to map areas of plant growth?
    • What NASA instrument (sensor) gathers information on vegetation? What does the sensor measure to determine the amount of vegetation?
    • The MODIS instrument is the Vegetation Index sensor. It measures how much light is reflected and absorbed by plants. Actively growing healthy plants absorb red and infrared light. They reflect near-infrared light. By combining this information scientists are able to determine areas of plant growth. The values range from -0.1 to 0.9.

  8. Close the description window when done.

Step 3 – Explore the NEO Map Interface Buttons and Tools

  1. Examine the homepage (Blue Marble) image and learn how to navigate the View. The top three buttons in the upper left allow you to control your view of the image. Click the ? button to find out how the buttons and tools work. Then use them to zoom in on a place that you know. When you click the ? button, you get a pop-up box with all the buttons and tools described. Click the X in the upper right-hand corner to close the Map Widget Help box.

    1. Click the (+) button to zoom in on the View.
    2. Use the Drag tool to pan (move) around.
    3. When you are done, use the (-) button to zoom out or the (=) button to zoom to the full extent of the View.

  2. Zoom in on a place you are interested in.
  3. The limitation of not being able to see many details in the image demonstrates the concept of an image's spatial resolution. Each picture element or pixel in the image represents a square area on Earth's surface that is 11 km on each side in this particular image. This is a relatively low spatial resolution image.

Step 4 – Download a Year of Monthly NDVI Data

Temporal resolution is a term that describes the time interval of the data. These vegetation index data have been averaged over different time periods, so the user has a choice of monthly, 8 day, or 1 day averages. Monthly is a good choice for an overview of a year's patterns. Daily images might be better to view an intermittent event at high resolution, like the spread of a wildfire or a rainfall event.
  1. Before you begin, create a folder named NDVI 2010 to hold the twelve images you will download.
  2. Open the NASA Earth Observations (NEO) homepage .
  3. In the list of Life datasets, click Vegetation Index. This will display the most recent Vegetation Index image in the main window, and list available data sets in the Search Results window.
  4. Use the Next link at the bottom of the Search Results to find and download the January 1, 2010 to February 1, 2010 image at a resolution of 0.5 degrees and save it as 01_NDVI_2010.jpg. Repeat the process for all twelve months of 2010 until you end up with a total of twelve images, named from 01_ NDVI_2010.jpg to 12_ NDVI_2010.jpg.
    1. Use the Next link at the bottom of the Search Results to find the January 1, 2010 to February 1, 2010 dataset and use (+) and View to display the image. In the Download Options box, change the selection from Full to Resize. Then select a fixed resolution of 0.5 degrees. Click the Get Image button to render the image.

    2. The rendered image opens in a new window. On a PC, right-click on the image and on a Mac, control-click on the image to download and save it. Do not change the file format, keeping the image as a jpeg. Save the image into the NDVI_2010 folder you created and name it 01_NDVI_2010.jpg. (Note: the syntax is a zero, 1, underscore, etc. "01_")
    3. Click the (+) and then View to display the February 1, 2010 to March 1, 2010 image. Use the same procedure as above to Resize, Get Image and save the rendered image with a fixed resolution of 0.5 degrees.
    4. Save the second image, naming it 02_NDVI_2010.jpg in the NDVI_2010 folder.
    5. Use the Prev button at the bottom of the Search Results to access the remaining months from 2010. You should end up with a total of twelve images, named from 01_ NDVI_2010.jpg to 12_ NDVI_2010.jpg.
  5. You need all 12 images to perform Part 5, Animate NEO Data with ImageJ. If you had difficulty obtaining the images from NEO, then download and save the ones here below into your NDVI_2010 folder. Click the thumbnail to open the full size image in a larger window. Then right-click (control-click Mac) to choose file Save Image As... Do not rename the files. Keep them as 01_NDVI_2010.jpg, 02_NDVI_2010.jpg, etc.

  6. ndvi 1 January 2010

    ndvi 2 February 2010

    ndvi 3 March 2010

    ndvi 4 April 2010

    ndvi 5 May 2010

    ndvi 6 June 2010

    ndvi 7 July 2010

    ndvi 8 August 2010

    9 September 2010

    10 October 2010

    11 November 2010

    12 December 2010

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