
With at least two GPSs, students can engage in a fun activity to literally measure the circumference of the Earth!
For two versions of lessons on this, see the attached files.
Measuring the Circumference of the Earth by Joseph Kerski, ESRI K12 Education
This is a fabulous lesson with many extension.
Measuring the Circumference of the Earth by Diana Papini Warren, Women in Technology
This is a simplified version of Joseph's lesson with easy to use tables for the calculations!
MeasureCircumference_Papini.pdfMeasureCircumference_Kerski.pdf