Teaching Notes

Example Output

Example Output
Distances across the widest portion of the Aral Sea in September of 2001 and 2003. Click on image for a larger view.

In this chapter, students will select from a series of images and will measure changes in the area of the lake and distance across the lake using ImageJ. The images, right, show one example of the types of images and output from this chapter.

Grade Level

The technique, tool, and datasets are appropriate for use by students in grades 7-14.

Learning Goals

After completing this chapter, students will be able to:

  • download, install, and use ImageJ image analysis software to quantify change over time in satellite images;
  • access and download satellite images for specific locations and times;
  • set a scale (spatial calibration) for an image in ImageJ; and
  • select and measure distances and areas on images in ImageJ.


People often have trouble interpreting features in satellite images because they are unfamiliar with the scale at which they are viewing the features. The ability to measure these features and see the results in real-world units gives students a way to check their actual size, assisting them in the task of interpreting what those features are.

This technique can be also be used to quantify the study of satellite images. For images that show change over time, the amount of area that changed between successive satellite images can be measured, graphed, and analyzed. Because the dates of the satellite images are known, rates of change can also be calculated.

Background Information

More about Satellite Images

Satellite images are composed of a rectangular array of pixels, or picture elements. Each pixel represents a single measurement made by a satellite instrument, and each measurement corresponds to a specific amount of area on Earth's surface or in the atmosphere. Though we are limited to measuring across pixels on a satellite image, knowing exactly how much area is represented by each pixel allows the image analysis program to convert from pixels to real-world units. To set the spatial calibration or scale of an image, students enter the desired units of measure and a conversion factor that indicates the distance on the ground represented by each pixel in the image.

More About the Aral Sea

The following links may be of interest to teachers and students:

Science Standards

The following National Science Education Standards are supported by this chapter:

Grades 5-8

  • Use appropriate tools and techniques to gather, analyze, and interpret data.
  • Communicate scientific procedures and explanations.

Grades 9-12

  • Use technology and mathematics to improve investigations and communications.
  • Scientists rely on technology to enhance the gathering and manipulation of data.
  • Interactions among the solid earth, the oceans, the atmosphere, and organisms have resulted in the ongoing evolution of the earth system.

Geography Standards

The following U.S. National Geography Standards are supported by this chapter:

  • How to use maps and other geographic representations, tools, and technologies to acquire, process, and report information from a spatial perspective
  • How to analyze the spatial organization of people, places, and environments on earth's surface
  • The physical processes that shape the patterns of earth's surface
  • How human actions modify the physical environment

Time Required

  • Case Study: 5 minutes
  • Part 1: 20 minutes.
  • Part 2: 10 minutes
  • Part 3: 10 minutes
  • Part 4: 20 minutes

Other Resources

Teaching Resources

The following files may be used in class to save time downloading and stacking images. This completed spreadsheet file can be used as a sample, or as a way to assess student work for the optional section described in Part 3, Step 4. Note: student results may vary depending on where they selected a region to measure.