# Measuring the Earth Project - General Procedure

Preparation
 To do this experiment you will need some materials to measure shadows accurately. Your "gnomon" will be a meter stick that is perpendicular to the ground. For your measurements to be accurate, it is critical that the meter stick be vertical. (Note the devices used below. Wind can be a major factor. Just ask Kathleen Smith. She held a contest to see which group could come up with the sturdiest measurement station.)
 Saint Andrew's Catholic School  Fort Worth, Texas Manasquan High School  Manasquan, New Jersey
Chart 1
 Site Location on globe -  latitude Location on globe - longitude Shadow length Sun angle (Your school's name goes here) . . . .
These values are entered into the central data base for this project. (Details explained at site.) Choose shadow lengths data from other sites. Inform these sites that  you using their data.

 You might want to make a chart and place it next to a wall map of the world. Use the map to mark where the participating schools are located.

Chart 2
 Site Location on globe -  latitude Location on globe - longitude Shadow length Sun angle your school . . . . school #1 . . . . school #2 . . . . Etc. . . . .

After you have several schools with entries, the students pick out one of the schools to complete the chart with. Have your students extend the chart to include the central angle, circumference, and percentage error.

Chart 3
 Site Location on globe -  latitude Location on globe - longitude Shadow length Sun angle "Center of the earth" angle N/S Distance Circum- ference % error your school . . . . . . . . school #2 . . . . . . . . School #3 . . . . . . . . Etc. . . . . . . . .

Now that you know the central angle, draw the location of your school and another school on the circumference of a large circle.

• Determine how many "slices" fit into this circle.
• Use the north-south distance to determine the value of the circumference. Explain why that works.
• Calculate the percentage error. (Use 40,000 kilometers as your benchmark.)
• Repeat the same process for a different school.
• Call up the website that contains the calculations and see how well you did. Confirm your calculations with the spreadsheet values.
• Create a web page describing the activity and what you and your students learned from doing this project.
• Link your webpage to the Noon Day "quilt" (See details at the discussion area.)
(Optional approach: Use trigonometry to determine the sun's angle.)