Hawai'i Space Grant College, Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, 1996

Digital Images
Purpose

To simulate, by hand, how a computer may process digital images into color pictures and to learn how a planetary geoscientist interprets these pictures.

Key Words

digital numbers

rows

columns

picture elements or pixels

gray-scale

color

palette



Materials

digital image activity sheet

colored pencils:

red, orange, yellow,

green, and blue

 Senario
Travelling through space, you are approaching the third of nine planets whose orbits center on a medium-sized star called Sun. One of your electronic scanning instruments has produced an image in digital form. Unlike a camera, your instrument has not produced a simple photograph of the planet's surface. Instead, you have rows and columns of numbers.

Just as you are about to process the digital image on your computer, there is a massive electrical discharge of unknown source. Your onboard remote sensing instruments and computers go out.

Your crew's exploration mission is in jepordy unless you can process the image by hand and interpret the results before it's too late.

Procedure

1.
Notice that the digital image has rows and columns of numbers in squares of equal size. When assigned gray-scale brightness or color values, the numbers become picture elements (also called pixels) which together form the whole picture.

What is the color palette for this image?

1=

2=

3=

4=

5=




2.
Color the digital image according to the palette.

3.
What are you looking at? What do you recognize?

4.
What do the colors mean? That is, what information is the image revealing about the surface of the planet?

5.
Does the size of the squares affect how much information you can interpret from the image? How?

6.
If you could take another image with this scanner, then how could you get more detailed information?

7.
Everything you know about the surface of the planet is based on your interpretation of this image. Now, would you land your spacecraft on this place? Why or why not?

8.
What other informtion about this place could you gather from your remote sensing instruments before making a decision to land?


Go to Digital Image activity sheet.
Go to Digital Images Teacher pages.
Return to Remote Sensing Activity Index.
Return to Hands-On Activities home page.
http://www.spacegrant.hawaii.edu/class_acts/