Unit 1: Collecting GPS Data
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This page first made public: May 28, 2019
GPS data can measure vertical and horizontal bedrock motion caused by a variety of geologic processes, such as plate movement and the changing amount of water and ice on Earth's surface. In this unit, students will learn the basics of how GPS works and how to read GPS time-series data.
Unit 1 Learning Outcomes
- Students will be able to explain how high-precision GPS data are interpreted
- Students will calculate the horizontal speed and direction (within a reference frame) of a GPS station using data provided as time-series graphs
The Learning Outcomes for Unit 1 support Module Goal 1.
Earth Science Big Ideas(link opens in new window)
ESBI-1: Earth scientists use repeatable observations and testable ideas to understand and explain our planet.
ESBI-4: Earth is continuously changing.
Unit 1 Teaching Objectives
- Cognitive: Promote an understanding of the relationship between bedrock motion and resulting time-series graphs; give students a description of how high-precision GPS stations work and have them apply that knowledge to considerations when installing a station
- Behavioral: Promote skills development in reading and interpreting bedrock GPS time-series data and understanding its relationship to reference frames; provide a framework for students to approach data reading and interpretation to solve problems like a scientist; give students opportunities to identify trends and calculate rates
- Affective: Encourage a level of comfort with using quantitative skills to solve problems; encourage an appreciation of the usefulness of GPS data to society
Context for Use
The content for Unit 1 is appropriate for introductory geology, historical geology, oceanography, environmental science, and other geoscience courses; sophomore-level courses in which geodesy is being introduced; or non-geoscience courses where the nature and methods of science are being investigated. Unit 1 activities can be used in small- to medium-enrollment classes and adapted to serve large-enrollment classes. They are designed to be flexible in their context and can be executed in lecture and lab settings as an in-class activity or the beginning of a collaborative lab exercise.
In the Measuring the Earth with GPS module, this unit can be used as an introduction to one or more of the other units by developing skills and an understanding of the GPS data that students have the opportunity to then build on in subsequent units.
For some courses, it is also possible to just use the presentation about GPS from Unit 1 as an introduction to one of the other units and then go straight on to a later unit without fully doing the Unit 1 exercise. This would probably be a good idea only if your students have more experience with time-series and graphs.
Description and Teaching Materials
Introductory Lecture (15–30 minutes)
This brief interactive lecture introduction provides context for Measuring the Earth with GPS by introducing students to:
- How GPS works with Think-pair-share questions and ConcepTest questions
- Think-pair-share asking students to think about how studying GPS motion can be useful to society
- Brief directions for the Jigsaw activity, below
- Think-pair-share questions asking students to make observations and interpretations about GPS time-series graphs
Slides: Unit 1 Introductory slides (PowerPoint 2007 (.pptx) 11.9MB Jul11 19)
Optional Introductory GPS Handout for students:
- This two-page document can help students record their notes on how GPS works.
For additional details on how GPS works: See the majors-level Introduction to GPS presentation (majors-level) (PowerPoint 2007 (.pptx) 30.6MB Jul11 19) from GPS, Strain, and Earthquakes > Unit 3: Getting started with GPS data
Jigsaw (45–60 minutes)
In this activity, students will use the Jigsaw technique to learn to quantitatively interpret GPS time-series graphs. Students initially form three teams, each team specializing in one of the following: reference frames, direction of motion, or speed of motion. After students complete a short, one-page handout about their specialization, they re-form into groups, with each group member representing one of the teams. In their new groups, students apply their knowledge to interpret a GPS time-series graph and calculate the speed the station is moving. Each group can work with data from the same GPS station, or different groups can each work with data from different stations. Data are provided for eight stations, although instructors (or students) can easily download graphs from the PBO Network Monitoring website. (Accessing PBO GPS data: 1-page info sheet (Acrobat (PDF) 308kB Jun17 18))
Student activity handout:
- Student version:
- Activity 1.1 Student Exercise: Jigsaw (Microsoft Word 2007 (.docx) 3MB Jul9 19)
- Activity 1.1 Student Exercise: Jigsaw PDF (Acrobat (PDF) 3.6MB Jul9 19)
- Student graphs:
- Graphs for Jigsaw Activity (Microsoft Word 2007 (.docx) 4.9MB Jun30 19)
- Graphs for Jigsaw Activity PDF (Acrobat (PDF) 4.7MB Jun30 19)
- Instructor version with rubric:
- Students complete all the handouts in small groups, working with the same group the entire time; each group can use different GPS data
- Students complete the three team handouts as homework, and then work in class in small groups to apply their knowledge to the GPS data
- Students complete the three team handouts (in class or as homework), and then do a gallery walk to interpret data from different GPS stations
- Instructors may need to provide additional scaffolding and structure if students complete the sheets as homework, since some of the students may struggle with the concepts. For example, the instructor may want to display one of the example GPS plots and do a think-out-loud of how they view the data (in terms of determining the reference frame, the direction of motion, and the speed of motion). Or, the instructor may wish to add some think-pair-shares to help the students before they work individually.
Teaching Notes and Tips
- Be sure to emphasize the "coolness" of knowing how the GPS in their phones works. That gets their attention. Also make sure they understand the math they are practicing in this unit is important in other units coming later so they see the reason behind it.
- Eight data sets from example GPS stations are included in the instructor version of the handout. Other stations can be found at the PBO Network Monitoring website, and it is easy to download graphs in the same format.
- Instructors can build on this activity by having student compare their results of different stations across the country. This can lead to a discussion of tectonic plate movement.
- Instructors can also follow up this activity by showing the GPS Velocity Viewer, which can display vectors illustrating station movement. Students can compare their stations to what is displayed. You are also able to change reference frames.
Unit 1 can be assessed formatively by using some of the questions as prompts for discussions. In addition, if the students are working in class or lab on the questions, the instructor can circulate and listen to student conversations and answer questions to ensure that the desired learning is occurring.
The Jigsaw group activity can be used as the summative assessment for this unit (Unit 1: Collecting GPS Data), if desired. Instructors can also have students complete the group activity using a different GPS data set than what they used during the Jigsaw activity.
References and Resources
Additional Resources for Instructors:
- GPS stations with graphs can be found at: PBO Network Monitoring
- The GPS Velocity Viewer displays vectors illustrating station movement
- More information about reference frames can be found in additional details in the GPS Velocity Viewer Reference Frames
IGS08 is a 'no net rotation' reference frame. 'No net rotation' is the motion of each plate with respect to the weighted average of all of the world's plate velocities. It is sometimes referred to as absolute plate motion, since it appears to approximately represent the motions of the surface plates with respect to the Earth's deep interior. It closely resembles the apparent motion of the world's plates with respect to hot spot volcanoes. The student activity describes it as the reference frame defined by hot spot volcanoes for simplicity.
- Here is a key relating GPS graphs and vector direction
- Here is a discussion of Time-Series Plots
- Additional learning resources and modules for GPS can be found on UNAVCO's Tutorials and Handouts page
- This website give GPS basics