Steven Skinner: Using High Precision Positioning with Static and Kinematic GPS/GNSS in Geophysics for Geologists at California State University-Sacramento
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About this Course
This is an upper division elective for geology majors.
15
students
Two 75-minute lectures per week
G112 Syllabus (Acrobat (PDF) 77kB Dec26 18)
Introduction to the principal geophysical concepts and techniques useful to geologists in the study of tectonics, the Earth's interior and resource exploration. Includes the study of seismology, heat flow, gravity, borehole geophysics, electromagnetism and geodynamics.
Students will be able to quantitatively solve problems of gravity, heat flow, magnetics, and seismology. They will develop an intuition for how these properties vary based on geologic structure. Students will understand the structure of the Earth and how we can determine the structure through geophysical methods.
My geophysics for geologists course is an elective for geology majors and provides a broad overview of global and applied geophysics. Currently the course consists of 75 minute lectures twice a week. Exercises were distributed throughout the semester and sometimes had to be split over multiple class periods or take place on a weekend 'field day'. One of learning objectives of this course is for the students to be able to design an appropriate geophysical survey with an understanding of how equipment and sampling distribution influence resolution. This year we added the GNSS exercises to the usual seismic and magnetic surveying. The students all enjoyed the GNSS exercises in part because it is an extension of something they carry around in their pockets every day.
Each group thought they had come up with bulletproof strategy for topographic data collection. Students were amazed to see how much the final surface models varied based on the sampling strategy used in the field.
My Experience Teaching with GETSI Materials
As there are not any faults scarps on our campus, we used the American River levees and a staircase as a training ground for developing sampling strategies.
Relationship of GETSI Materials to my Course
My course is 15 weeks long and the units were used throughout the semester. The accuracy-precision-error exercise was used early in the semester when we discuss the limitations of data. The kinematic GPS exercises were used toward the end of the semester after we had discussed spatial and temporal filtering. The timing was also constrained by the availability of equipment, which we only had for a couple weeks of the term. Because we only had one base station and one rover, I made myself and the equipment available for two weekends and the students came in groups of 2-3 to measure topography. Working with the students in small groups was key to the success. Having one rover and running the exercise multiple times was probably easier than trying to troubleshoot multiple rovers at the same time.
Unit 1: GPS/GNSS Fundamentals
- Introductory lecture to GNSS
- Accuracy-Precision-Error exercise
- Without a survey grade instrument to compare our data to, we created two groups of recreation grade receivers and placed them a measured distance apart.
- Concept Sketch Assessment
Unit 2: Kinematic GPS/GNSS Methods
- Kinematic GNSS lecture
(Omitted Unit 2.2 Change Detection)
Unit 2.1: Measuring Topography
- Student Exercise: Creating topographic surfaces in ArcMap
- We used the Salmon Falls map and data as an introduction to sampling strategy and surface creation
- Summative Assignment: Measuring topography with kinematic GNSS
- Groups surveyed levees and a staircase on campus and used their imaginations to be part of a team measuring offset along a fault scarp after a major earthquake.
Unit 3: Static GPS/GNSS Methods
- Static GNSS lecture
- Student Exercise: Introduction to GNSS Time Series – Borah Peak, ID
Assessments
All of the exercises and assessments were well received by the students. The summative assignment of measuring topography was probably the biggest eye opener for most of them as they realized the sampling strategies were for the most part insufficient to reproduce the observed topography. The next time I used this module I will have them measure the topography, create the surface in ArcMap, and then give them the opportunity to do an additional survey and adjust their sampling based on the outcomes of the first iteration.
Outcomes
All of the students had a basic understanding of GNSS through their smart devices and were enthusiastic about the opportunity to use a higher-grade instrument. My main goal was for the students to understand the limitations of data and how to design a survey to best address a geologic problem. They all became very aware of the limitations of the system as they tried to measure topographic steps. In the end all were comfortable operating the equipment and aware of the necessity of good survey design.
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