Measuring Ground Motion with GPS: How GPS Works

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

This activity is part of the On the Cutting Edge Exemplary Teaching Activities collection

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This page first made public: Feb 27, 2022

Summary

This activity helps students better understand how GPS measures ground motion. Students work with models of GPS stations and printouts of typical GPS velocity vectors found near different tectonic boundaries.

GPS velocity vectors point in the direction that a GPS station moves as the ground it is anchored to moves. The length of a velocity vector corresponds to the rate of motion. GPS velocity vectors thus provide useful information about how Earth's crust deforms in different tectonic settings.

Geospatial, Geodesy, Tectonics | Middle (6-8), High School (9-12), College Lower (13-14)

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Context

Audience

This demonstration can be used with middle school, high school, and introductory undergraduate students, as well as free-choice learning environments.

Skills and concepts that students must have mastered

Learners should have a general understanding of GPS. Learners should also have some familiarity with the concept of plate tectonics.

How the activity is situated in the course

This demonstration is particularly useful when discussing plate tectonics, plate boundary types, and the use of GPS to measure ground motion. This demonstration is expected to take 5 - 15 minutes.

Goals

Content/concepts goals for this activity

Earth's surface is constantly in motion.

GPS can be visualized as velocity vectors.
A velocity vector points in the direction that a GPS station is moving and its length is proportional to the rate of motion.
Velocity vectors from GPS data show how Earth's crust moves in different tectonic settings.

Higher order thinking skills goals for this activity

Discuss relative movement of tectonic plates such as the Pacific and North American plates in California, using GPS data

Other skills goals for this activity

Not applicable

Description and Teaching Materials

Supplementary Materials: Map Examples (Zip Archive 17.7MB Nov12 21)
Supplementary Materials: Tectonic Setting Maps and Scenarios (Zip Archive 286kB Nov12 21)
Measuring Ground Motion with GPS Writeup (Acrobat (PDF) 50kB Nov12 21)

Teaching Notes and Tips

A complete run through of the demonstration can be found on the UNAVCO YouTube Channel.

Assessment

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