ctivities
Day 3
In this exercise, the method for producing a satellite-generated image will be studied.
The concept of computer enhancement will be introduced, but instead of using a
computer, the student will generate an image on a piece of graph paper superim-
posed upon a map of the eastern U.S. seaboard.
Students should imagine a broadcast of infrared data from a NOAA satellite on a
descending orbit from the North Pole in the morning hours. An area is observed by the
satellite as a series of temperatures, the information is encoded, and sent as radio sig-
nals. When the signal is received by an Earth station, the radio signals are decoded
and displayed on a computer monitor. The image (this is not a photograph) produced
is actually made up of thousands of tiny squares called picture elements or.
Each pixel is assigned a number value between 0 and 255. The number assignments
are determined by the temperatures that were measured by the NOAA satellite sensors
during its pass. In this system:
0 represents pure black (warmest)
255 represents pure white (coldest)
all values in between are shades of gray.
The value of each pixel is electronically transferred as a byte. A is a unit of eight
bits of data or memory in microcomputer systems. is a contraction of binary digit,
which is the basic element of a two-element (binary) computer language.
Provide each student with:
- a Computer Simulation worksheet
- the Scanner Map Shading Chart
- a Student Scanner Map composed of 26 squares by 34 lines to re p resent 884 pixels
Students will use colored pencils to shade in each square (pixel) according to the sug-
gested color code on the map and on the shading chart. They should note their start
and completion times to enable them to calculate their rate and compare it with a
NOAA satellite rate. It is important that they shade in one row of the image at a time,
beginning at the top, since they are simulating a satellite descending from the Nort h
Pole. When the image is completed (p. 207) students should observe the familiar geo-
graphical features of the United States with a large cold front and its associated
f o rmation over the Ohio Va l l e y. A comma cloud is a band of cumuliform clouds
that look like a comma on a satellite image. Make several transparency copies of the East
coast map on the preceding page to help students locate the weather pattern s.
Answers for Computer Simulation Worksheet
- 640 pixels x 480 pixels = 307,200 pixels
- 24 pixels x 36 pixels = 864 bytes = 6912 bits
Answer for extension
The binary code equivalent of 80 is 01010000.
SI M U L AT I N G CO M P U T E R
IM A G I N G SO F T WA R E
A
