Pinpointing Location with GPS Demonstration

Shelley Olds (EarthScope Consortium), Daniel Zietlow (UNAVCO), & David Thesenga (Alexander Dawson School)

EarthScope Consortium logo. Concentric circles in red grading to purple.

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Using string, bubble gum, and a model of a GPS station, demonstrate how GPS work to pinpoint a location on Earth.

Precisely knowing a location on Earth is useful because our Earth's surface is constantly changing from earthquakes, volcanic eruptions, tectonic plate motion, landslides, and more. Thus, scientists can use positions determined with GPS to study all these Earth processes.

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This demonstration can be used as an extension to an introductory earth science course.

Skills and concepts that students must have mastered

Students should have a general understanding of GPS.

How the activity is situated in the course

This demonstration can be used at any time in an earth science class, though is particularly useful when discussing how GPS works. This activity needs 5- 15minutes, depending on questions and extensions into an activity about GPS.


Content/concepts goals for this activity

  • GPS satellites send a signal with important information that can be used by GPS receivers on the ground.
  • How long a signal takes to reach a GPS receiver tells us distance between a satellite and GPS.
  • Measuring position in this way is called trilateration.
  • We need four satellites to find and pinpoint the precise position.

Higher order thinking skills goals for this activity

Interpret the intersection of spheres in 3-dimensions.

Other skills goals for this activity

Description and Teaching Materials

Teaching Notes and Tips

A complete video of the demonstration can be found on YouTube.


Students describe and sketch what have they learned from the demonstration.

The exercise includes sample questions the learner could answer. These can be used for formative assessment of understanding or they can be graded on a simple 2-point scale:

  • 2 points = correct answer with thorough supporting evidence and/or complete description
  • 1 point = answer not completely correct or lacking thorough supporting evidence or description
  • 0 points = incorrect answer

References and Resources