Purpose:

The purpose of this activity is to have the students generate a raster image by hand.

Materials:

graph paper, lab hand-out, newspaper article, enlarged newspaper article, pencils

About this activity:

This activity involves a laboratory investigation and a teacher demonstration. The investigation shows how digital information is received and translated into an image.

Procedure:

1. Explain that images are composed of pixels. Pixel - a picture element that produces a single dot of color. The remote sensing sensor divides the earth into blocks or pixels. Each pixel is recorded as a brightness value from 0 - 255. These numbers are the data which are transferred with a computer.
2. Show the students a picture from a newspaper. Have them make observations. Then show the students the same article, but enlarged. The students should notice the blocks of different shades of gray. An image is made up in the same way.
3. Divide students into pairs for this activity. Students will use a gray scale to make an image from data.
4. Pass out the lab hand-out.
5. When the students finish the activity have them compare their pictures with their classmates. Discuss the results of the activity.

Name________________________________ Date______________

Activity for Processing Remote Sensing Images

Purpose:

To use a gray scale to take data and make an image from that data.

Materials: (per group)

• graph paper and a pencil

Procedure:

1. Below is a gray scale you will use to get your information.

   Shade of gray	black	darker gray	dark gray	gray	light gray	pale gray	faint gray	off white	white
   Digital Value	0	32	64	96	128	160	192	224	255

   This is the gray scale you will use for your shading. These are given in intervals. If you have a number that is between intervals, estimate what you think the shading would look like.

2. Below is a list of values for your image. Each number represents one block or pixel on the graph paper. Do not skip spaces. For example, if you are given the number 255, you are to leave that white just like your scale above shows.

   255	255	255	200	200	200	200	200	255	255	255
   255	255	200	130	090	090	090	130	200	255	255
   255	200	130	130	090	090	090	130	130	200	255
   200	130	130	130	032	000	032	130	130	130	200
   255	200	130	130	090	090	090	130	130	200	255
   255	255	200	130	090	090	090	130	200	255	255
   255	255	255	200	200	200	200	200	255	255	255

3. Begin composing your image. It does not matter where you start as long as you leave enough room to fit the entire image on your graph paper.

Conclusion Questions:

1. Do you think this scale was effective in displaying an image? Explain your answer.
2. Using the same gray scale select numbers that would show an image or a design. Your image must have at least ten rows and ten columns. You may use the same sheet of graph paper or use another sheet of graph paper if you have a larger image.

   Show your data below in the space provided.

3. Describe some of the difficulties you came across when making your own image.