Digital Images

Students will learn about digital images and how satellites orbiting Earth send information and pictures to Earth over the Internet.

By completing these activities over a one week period, the learner will:

use a digital camera to put pictures on a computer
observe magnified digital images
use graph paper to create digital information
create an information transfer protocol
design encrypted messages or pictures
as a team, decode a satellite image from space
discuss ways to improve digital image resolution and accelerate information exchange

National Science Education Standards

National Mathematics Education Standards

Materials and Technology

Scientific Background

Activity 1: Investigate how electronic information is transferred over the Internet and displayed on computers by viewing pictures on the computer.
Activity 2: Create an image of your name by blacking-out individual squares on rectangular graph paper.
Activity 3: Discuss "binary systems" and create a "mystery word" or "mystery picture" on graph paper. "Tell" a fellow student how to recreate this picture WITHOUT showing him or her the picture.
Activity 4: NASA Imaging Teams recreate a picture of our Sun by translating binary data sheets.
Debriefing:Discuss RESOLUTION and DATA COMPRESSION ROUTINES to increase the speed of image processing.

Activity 1: Anticipatory Set (Day One)

Take pictures of students or your school and observe them on the computer (use either a digital camera or scan images taken with a conventional camera). Ask students how the picture or information to make the picture got inside the computer. Other pictures students should be shown include daily weather satellite images. Tell students that the class is going to learn how electronic information is transferred over the Internet and displayed on computers.

Go back to Activities.

Show each student a magnified image of his or her picture on the computer. Excessive magnification will show that an electronic picture is composed of little squares, called picture elements or pixels. Ask students to examine the image and count the number of pixels. For example, you might ask them how many pixels wide some image is, or some part of that image: a face, a nose, a chair, etc.

Activity 2: Exploration (Day Two)

Direct students to create images of their names by blacking-out individual squares on rectangular graph paper. There should be no shading or "half-squares" colored in. First color in the squares; second, add numbers to identify colors. Provide students an example, such as the one shown below.

Go back to Activities.

Two Color Image ( 0 = White; 1 = Black)

1	1	1	0	1	1	1	1	1	1	1	1	1	0	0
1	0	0	1	0	1	0	1	1	1	0	0	1	0	0
1	0	0	1	0	1	0	1	1	1	0	0	1	0	0
1	0	0	1	0	1	0	0	0	1	0	0	1	0	0
1	1	1	0	0	1	0	0	0	1	1	1	1	0	0
1	0	0	0	0	1	0	0	0	1	0	0	1	0	0
1	0	0	0	0	1	0	0	0	1	0	0	1	0	0
1	0	0	0	0	1	0	1	1	1	0	0	1	0	0
1	0	0	0	0	1	0	1	1	1	0	0	1	0	0
1	0	0	0	1	1	1	1	1	1	1	1	1	1	1

(rows are horizontal and columns are vertical)

Activity 3: Concept Introduction (Day 3)

Computers often record and transfer information using a series of ones (1) and zeros (0). This is called a "binary system." In the images that students created, a computer would often record each box or PICTURE ELEMENT (pixel) as being a zero for white and a one for black.

Go back to Activities.

1	1	1	1	0	0	0	0	0
0	1	0	0	1	1	1	1	1
0	1	0	1	1	0	1	0	1
0	1	0	1	1	0	1	0	1
0	1	0	1	1	0	1	0	1

Ask students to create a "mystery word" or "mystery picture" on graph paper and "tell" fellow students how to recreate exactly the same image WITHOUT showing students the picture. Call white squares zero and black squares one. Suggest to students that they start in the upper left hand corner of the paper and read numbers (one and zeros) all of the way across the page to the end of the line, then going back to the left side to read the second row, third row, and so on.

Students should try to and create, if possible, ways to speed up the process of telling someone how to create the picture. (When scientists create ways to speed up the process, it is called FILE COMPRESSION).

Activity 4: Concept Application (Day 4)

Satellites send images from space to Earth by radio waves using a series of ones and zeros. In this activity students will decode an actual image from the Yohkoh satellite (http://solar.physics.montana.edu/YPOP/). The process of sending data from a telescope to the Internet is called TELEMETRY.

Divide students into four or eight NASA imaging teams. Each team needs one of four attached data sheets, a sheet of graph paper, a black marker, and a pencil. IMPORTANT: Students should read across rows, one row at a time. Encourage students to figure out ways to make the process go faster, but keep in mind it is very important to be as accurate as possible.

Team
Two Team One

Team
Three Team Four

Overlay the teams’ images as shown at left with no gaps in the data. These four quadrants should combine to create an actual image of our Sun taken by the X-ray telescope on board the NASA and Japanese Yohkoh satellite. The black spots show the most active regions of our Sun that generate X-rays. These energetic regions are places where sunspots can often be observed. Additionally, these areas are high energy regions that release particles that can be observed on Earth as the Northern Lights.

Go back to Activities.

Activity 5:

Digital images are recorded and transferred as pixels. The more pixels that are used, the better or more clear the image is (this is often referred to as RESOLUTION). However, the more pixels that are used to create an image, the more memory is required. Many images found on the Internet are 256 pixels long by 256 pixels wide.

How many pixels is that all together? (256 * 256 = 65,536 pixels)
Many satellite images are 512 pixels long by 512 pixels wide.
How many pixels is that? (512 * 512 = 262,144)
How long would it take you to read that many data points over the telephone (262,144 seconds is more than 3 days working 24 hours a day non-stop)?

This demonstrates one reason that scientists must work in teams - to split up the work so the final product can be finished faster.

NASA scientists are always trying to figure out ways to increase the speed of converting digital information into pictures. It is hoped that your students were able to come up with strategies to increase the speed of the process. Have your students share these DATA COMPRESSION ROUTINES.

Go back to Activities.

Investigate the software program that came with your scanner and/or digital camera. These programs will often let you INVERT pixels, change the number of colors allowed, and even MORPH pictures to change their shape. These are often powerful programs that users forget they own.

Also, any digital image from the Internet, scanner, or camera can be converted to a GRID of pixels. (Before you begin, use a graphic converter program (such as GraphicConverter for MAC or PaintShopPro for PC) to convert the image to PICT or TIF format if necessary.) Open the file using an image processing program (NIH Image for MAC or Scion ImagePC for PC) and EXPORT the file as TEXT. Then, the file can be opened in a spreadsheet program such as MS EXCEL.

Alternatively, any grid of numbers can be drawn in MS EXCEL by plotting a 3-D surface plot or by saving the data as TEXT and IMPORTing the data into your image processing program.

Assessment