In this step-by-step tutorial,
students will learn to use computer image processing techniques to measure
the size of Earth's polar ice caps and analyze various phenomena visible
on planetary images. These skills can be used to scale and analyze
any image of our Sun, the planets, or any other electronic image found
on the Internet.
By completing this activity,
the learner will:
find and download/save an image
of a terrestrial planet from the Internet
convert a GIF or JPG image to
use image processing software
to view and magnify the image
calibrate and scale the viewed
use the computer to measure the
diameter and area of polar caps
create a surface plot of the
1: Exploration of Earth's north pole.
2: Downloading, saving, and converting images
from the Internet.
3: Using image processing software for scaling
4: Class is divided up into NASA imaging teams
in order to present their discoveries of nearby
worlds using image processing
Let's look at a picture of
north pole. What do you see in this picture? What do the different
colors represent? Make a sketch of Earth's north pole; label the
continents and sketch the extent of the ice coverage. Predict how
the appearance of this area will change in the upcoming months, and add
this to your sketch.
- Downloading, saving, and converting images from the Internet
The concept introduction
portion of this lesson is presented as a step-by-step tutorial. It
is divided into two portions, each requiring one session using the computer.
In the first part of the lesson, students learn how to save images to their
computer's hard drive. In the second part of the lesson, student
learn how to scale and calibrate images in order to make measurements.
Any image that you find on
the Internet's World-Wide-Web (WWW) using Netscape or Microsoft Internet
Explorer can be saved on your hard drive for analysis. Even better, the
process is almost the same on a Macintosh or a PC. All you have to do is
1. Start your WWW
browser (Netscape or MS
Internet Explorer for example) and enter a URL that has lots of images
A great place to start is the NASA Windows to the Universe site at http://windows.engin.umich.edu/.
Some other fabulous places are NASA's Hubble
Space Telescope and Jet Propulsion
Laboratory WWW sites.
- Using Image Processing Software for Scaling and Measurement
2. To save an image to your
hard drive, position the mouse over the image and hold down the button
for a couple of seconds (use the right button if you have more than one).
3. A menu will appear and you
can select SAVE THIS IMAGE. This will give you an option about what
to call the image and where to save it. Note where it goes and what
it is called. Choose a different name and location if you like.
4. The image is now
saved on your hard drive and you can open it in the future with your WWW
browser or with any image conversion program you might have, like GraphicConverter
or PaintShopPro (more
information). With these programs, you can alter the image's
size, color, or even add text to the image as you wish.
5. Most images on the Internet
are in GIF (pronounced with a hard "g" as in "gift") or JPG ("jay-peg").
Image processing software do not typically use files in this format so
they must be converted to TIFF (which rhymes with GIF).
6. Use either Graphic
Converter or Gif Converter
(MacIntosh Compatible), or Paint
Shop Pro or L View Pro (PC Compatible).
From the file menu, select OPEN. Find the image that you downloaded
and open it using this converter program.
7. From the file menu, select
SAVE AS, and, in the format box, select save as TIFF format. Close
your graphics converter program and you are ready to conduct image processing.
1. If you haven't
converted your images to TIFF, you need to go back to part I and convert
your images to TIFF format.
2. Start your image processsing
software (MAC or PC
Using the FILE pull-down menu, select OPEN. Select the TIFF
image that you converted in Part I.
3. The first task is to calibrate
the image (tell the computer the scale of the image). If you are
looking at an image of Earth you must know the diameter (you can look this
up in a book or on the Internet
as 12,756 km). Using the segment tool (fifth from the top on the
right labeled "select lines"), draw a line across the diameter of Earth.
4. Under the ANALYZE menu,
select SET SCALE. Note that the computer has already recorded how
many pixels (picture elements) long the line you drew is. First,
change the UNITS to the known diameter units. Then, enter the known
diameter. For large numbers, like 93 000 000, use 93e6. Click
OK and your image is now calibrated. (example)
5. Use the magnifying glass
in the tool bar to focus in on the ice caps. The software will remember
the scale of the image, so you can get as close as you like to make a good
measurement. To un-zoom on a MAC, double click the magnifying icon
in the tool box; to un-zoom on a PC, use the OPT key on the keyboard.
6. Use the segment tool to
draw a diameter across the polar ice cap. From the ANALYZE menu,
7. From the ANALYZE menu,
select SHOW RESULTS. You might have to grab the bottom left hand
corner of the new window and expand the window to see your results.
8. Determine the diameter
for ice caps on several planets. How big are they?
9. You can use the same Freehand
Tool to Measure Perimeter and Area. This image processing program
has four tools for selecting regions for study.
The first tool in the right hand
column of the tool window is used to drag out rectangular areas.
The second tool in the right
hand column of the tool window is used to define oval or circular areas.
Using the third tool in the right
hand column of the tool window, you can connect a sequence of points with
line segments, to create a polygon of your own design. To close the
polygon (connect your last point to your first point), just click the mouse
twice in rapid succession.
10. Determine the area of an
ice cap using the freehand tool to trace the outside. Select ANALYZE
and SHOW RESULTS to view the measured value for perimeter and area.
The fourth selection in the right
hand column of the tool window allows you to freehand any curve you want
(this is called the Freehand Tool and looks like a heart).
Divide up into several NASA
imaging teams. Each team needs to analyze a different nearby
worlds and create a written technical report, a multimedia presentation,
and/or an oral presentation that describes:
and many others ..... A great
place to start is NASA's Planetary
Which images you analyzed.
How the images were analyzed.
How big are various features
compared to things on Earth or beyond?
The above process will work
on ANY image that you find on the Internet. Try out the following to demonstrate
your skills at image processing.
How far is it from your hometown
to the state capital? Find a map of your state, calibrate the
image using the map scale, and measure the distance by road between the
two places. How big is Jupiter's Red Spot ?
Use the known
diameter of Jupiter to calibrate your image. How big are Saturn's
rings? Use the known diameter of Saturn to calibrate your image.
Try the activities Dynamic
Martian Polar Ice Caps from NASA Project CERES, Measuring
Sunspots at the NASA Yohkoh Public Outreach (YPOP)
Olympus Mons, (the solar system's largest volcano) or Focus
on Hurricane Andrew (an enormous tropical storm) from the Network
Montana Project (NMP).
How do you determine the scale,
in order to analyze an image on the computer? Most
images on the WWW are in GIF or JPG format; what do you need to do in order
to use these image processing programs?