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Million Man March

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Summary of Article
It was one of the largest gatherings of African-American men in the United States, the Million Man March. But just how many people attended this historic march in our nation's capitol? This article explains how remote sensing technology was used to estimate the number of marchers. It offers a step-by-step explanation of how scientists count the number of people (or even animals) in large gatherings using satellite imagery. You will be able to view the actual photos that were used to help determine the official number of marchers.

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Suggested Age/Grade Levels
Age Level: 10 - 17
Grade Level: 5th grade - 12th grade

Related Topics
History
Discuss the civil rights movement in the United States.

Science and Technology

Discuss how science and technology aided in the advancement of remote sensing technologies.

Math

Discuss how the basics of mathematics were necessary to figure out the number of marchers.

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Objectives
After studying the article, students should be able to:

Discuss how remote sensing technology was used to determine how many people attended the Million Man March.
Discuss, in detail, how Dr. Farouk El-Baz and his team were able to count the number of marchers.

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Questions for Discussion
Q: What is one method Dr. El-Baz's team used to "count" the number of marchers?
A: To count the marchers, Dr. El-Baz and his team digitized 12 oblique 35 mm photos covering the march area near the Capitol, known as the Mall, and obtained a one-meter-per-pixel photo map of the Mall area from the Internet. Wherever possible, individuals' heads or shadows were tagged for a direct count.

Q: What did Dr. El-Baz and his team do when the area they were counting was too densely populated and they couldn't actually count how many people were there?
A: In areas where the crowd was so densely packed that it was impossible to count individuals, the density of people per pixel (six people in a one-meter square) was estimated, and used to calculate the density of similarly packed pixels. Dr. El-Baz was able to determine that six people could fit in a one-meter square by drawing a one-meter square and seeing how many people he could get to fit into it!
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Quiz
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Just the Facts
Dr. El-Baz used remote sensing technology to estimate the number of marchers at the Million Man March.

The Boston University team actually counted the number of people unless the area was too dense. At that point, the team estimated the density of people per pixel (six people in a one-meter square).

To check the accuracy of their count, Dr. El-Baz and his team also used some GIS software to estimate the density of marchers within a fifty-meter cell. The results were similar.

The Boston University team figured that there were 878,587 marchers. With an estimated error margin of 25%, the number of participants could have been as high as 1,098,234 or as low as 658,940.

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Links to Relevant Web Sites and Additional Resources

http://observe.ivv.nasa.gov/nasa/exhibits/march/march_6.html

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Vocabulary
pixel: a digital image is comprised of many tiny squares called picture elements, or pixels. Specific areas on an image can be located using the X and Y coordinates of the pixel. Each pixel is associated with a brightness value for the area of the image it represents.
remote sensing: the act of collecting information from something or about something not within reach. When you look at a faraway mountain you are remotely sensing it.

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For Fun
Just for fun, play our Million Man March Wordsearch game.
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