Photosynthesis Through Satellite Eyes - Activity 1

Photosynthesis Through Satellite “Eyes”

Activity sheet

Objectives

The students will describe how chlorophyll uses sunlight for photosynthesis. The student will analyze absorbed and reflected lights by looking at satellite images sensed with green, red and near infrared light.

Activities

In the CD you have received there are three 3 images. These images were sensed by LandSat 7 satellite.

Before you start using ArcView, let us understand the satellite images. You will see something like this:

What does this image represent?

It is what a sensor or “eyes” see. This image was recorded by a red sensor or “red eye”, so it shows what that specific satellite sensor saw at the time the “picture” was taken.

Each pixel has associated a number a shade and a number from 0 to 255.

Note that the image is in gray scale, you will not see the red color.

Black means the light was not reflected back (it was absorbed)

White that the light was totally reflected (it was not absorbed)

Different gray shades mean that some energy was absorbed some reflected.

Example:

If you are working with a image taken with a “red sensor”, which records the reflected red light, a black pixel means the red light was absorbed and white pixel means it was reflected.

You have three (or four) images like this, each of them were taken with different “eyes”. All of them are in gray scale; therefore you have to be careful and keep track of the image you are looking at.

Now explore your images!! … Follow these steps:

Open ArcView.
Open a new project.
Add themes, in the theme window select “Image data source” for Data Source Type and your CD driver. (See Figure 1).
Select Bgreen_W, Bred_W and BnearIR_W files (if you are working with summer, your images are Bgreen_S, Bred_S and BnearIR_S).
Make one theme active by clicking on the box next to the theme name and clicking on the theme name.
Save your Project! Use your initials.
Explore the images and try to identify differences among them.

References:

QUESTIONS

NAMES:

Winter Summer

Question 1: Can you identify vegetated areas? How? (Look for the shape of the different areas)

Question 2: Compare the red and near infrared values in the areas identified in question 1. If they are different, explain why.

Question 3: Focus in a small area in the green image (zoom in). Observe the shade of two pixels and plot them in the graph below (Place gray shades in between black and white). Then recognize the same pixel in red and NIR images; graph the shades and you will get a curve.

3-1 Are the curves you got similar to the plant signature?

3-2 Are there differences among the pixels? If yes, describe them.

Name:

Question 4: This is science fiction. You are in living in 2200. In 2100 human beings’ vision had improved. Now humans can see ultraviolet light as violet rays and near infrared energy as golden color. Describe how you would see your school back yard.