Back to the Teacher Resources Main Page

Part 2: Determining the Greenness Index

Guiding Questions: 

What patterns in greenness do I see over time in my digital images? How does this compare to the greenness measured by satellites?



**Note: the images and the ADI software will have to be unzipped and extracted before they can be used. Macs will do this automatically. To do this on a PC, right-click the folder, click Extract All and follow the instructions.**

    For more resources for learning about digital images and using ADI or similar software, see the Picture Post website or the Digital Earth Watch website

Estimated Time: 

What to do and how to do it:

  1. INTRODUCTION: Brief tour of the Analyzing Digital Images software, or watch the Analyzing Digital Images Video Tutorial. If appropriate, discuss the spectral components of a digital image (red, green, and blue bands). 
  2. Students use the Measuring the Greenness Index handout along with the provided Picture Post images, or images collected in Part 1 of this Sequence (if you do not have at least a few seasons of Picture Post images at your own site, you may want to use the provided images, or modify the activity to look at different image features – see Extensions below).  Alternative images can be used in this exercise as well. One great source of imagery is from the Phenocam Network. These tower (or building) mounted cameras provide a great view of the forest canopy, and can be used in this activity in a similar manner to those from the PicturePost network.To determine if there is a Phenocam near you, visit Follow this link to select and download a series of images to use in this exercise (provided from the Harvard Forest Schoolyard LTER program).
  3. WRAP-UP: Have students discuss the ‘Discussion Questions’ from the Measuring the Greenness Index handout in pairs or as a class. 


  1. Use the Checklist for Student Work, or your own rubric, to assess the quality of student work.
  2. Have students either informally report out to the class on the overall results/trends of their study (orally or using chart paper, the smartboard, etc.) or create a formal report. For suggestions, rubrics, and examples of formal reports, see the GLOBE Carbon Cycle Communicating Findings page.


  1. Have a poster board or excel data table and graph of the Greenness Index in your classroom that your students can add to each time you take a new picture at your Picture Post.
  2. Download a set of pictures from a Picture Post in a different location (all Picture Post images are available for free download from the Picture Post website)
  3. Use Analyzing Digital Images to compare different features of one image (How does greenness differ between the grass and a tree? What about the road?)
  4. Use Analyzing Digital Images to investigate how different features change over time (will you see the same patterns in greenness if you look at a deciduous versus a coniferous tree?). 
  5. Use the Greenness Index tool on the Picture Post website to analyze a small subsection of a digital photo across all photos in the archive. To do this, visit the Picture Post website, click on any Picture Post Page, and click the ‘make greenness index’ button on the right of the screen. Follow instructions to produce a graph of greenness.