Benjamin Crosby: Using High Precision Positioning with Static and Kinematic GPS/GNSS in GEOL 4407: GPS Applications in Research at Idaho State University
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Provenance: Ben Crosby, Idaho State University
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About this Course
Upper-division undergraduate course with mostly geology, geotechnology and environmental sciences students. A few students joined from history and the surveying program.
15
students
In-semester course. Two 3-hour Friday labs
GPS Applications in Research syllabus (PowerPoint 2007 (.pptx) 120kB Apr23 18)]
GEOL 4407 GPS Applications in Research (3 semester hours): Overview of satellite positioning systems usage. Topics include GPS theory, basic mapping concepts, use of mapping grade receivers for GIS data collection, and processing of carrier phase data for high precision applications. Prerequisites: GEOL 4403 (Principles of GIS).
Course Topics: Overview of satellite positioning systems usage. Topics include GPS/GNSS theory, accuracy and precision, sample design, spatial interpolation, mapping grade GPS collection and precise positioning using GNSS receivers.
Goals: After completing this course, each student should be able to design a GPS research project, collect/correct GPS data, enter the data into mapping software, conduct analysis of the data, and produce a final product to answer a scientific problem.
I taught two 3-hour labs focused on Kinematic GNSS/GPS for this academic-year GNSS/GPS-focused course. The labs from this module were about two-thirds of the way through the semester so students already had a good grasp of GNSS tools. I went straight to Units 2, 2.1, and 2.2 and the students were well prepared to learn this material. Units 2.1 and 2.2 were outdoor-oriented, doable within the time frame, successful from a student learning perspective, and led to significant student enthusiasm.
One student remarked, "I never imagined that collecting such high precision data would be so easy and enable such useful insights."
My Experience Teaching with GETSI Materials
Because I was testing Units 2, 2.1 and 2.2 in a GNSS-intensive course, I was able to skip directly to the Unit 2 introductory lecture instead of doing Unit 1 first. Students were well prepared for this. I used the same location and data set for the analysis in Units 2.1 and 2.2.
Relationship of GETSI Materials to my Course
The module was implemented two-thirds of the way through a semester-long course focused on GPS/GNSS. The equivalent of Unit 1 was already introduced to students before module testing began. The module material was not referenced again during the remainder of the course.
Unit 1: GPS/GNSS Fundamentals
Unit 2: Kinematic GPS/GNSS Methods
- Introductory Lecture for Unit 2 and 2.1
- Field introduction of the hardware to the students.
- Students generate a concept sketch describing the components and interactions between kinematic GNSS base and rover (this was essentially an adaptation of Unit 1 Summative Assessment exercise to just involve an RTK system).
Unit 2.1: Measuring Topography Students design a survey and then use RTK GNSS by setting up a base station and using 2 rovers to collect hundreds of points. Points are distributed across a landscaped concrete and grass landscape with both sharp edges and gradually smoothly varying topography.
- Students return to the lab and process their data to create interpolated surfaces. (A GIS course is a prerequisite for this course, which did speed up student ability to work in ArcMap, but is not absolutely essential.)
- Students describe the strengths and weaknesses of their sampling design.
Unit 2.1: Measuring Topography The two groups of students now have two topographic models of the campus topography. In order to recognize that even if the same location is surveyed, the distribution of points can create differences in the topographic model. Students are required to difference the two topographic models from each other and discuss whether the observed 'changes' are due to
- instrumental uncertainty (was the point elevation correctly collected by the GNSS?),
- interpolation errors (are the spaces between the points accurately described by the model?) or
- survey design errors (did we collect points in the same place? are the points we collected sufficient to represent the topography?)
- Summative assessment was accomplished through a synthetic report that included a discussion of both the generation of the topography and the surface-comparison exercise.
Unit 3: Static GPS/GNSS Methods
Assessments
The students enjoyed the synthetic reports that compared their two data sets and asked questions about what limitations there are to change detection if you are simply comparing topography. If there are not fixed monuments to measure, it is possible that the survey design (where you collect your points) will have a large influence over whether real topographic change is detectable or whether you only observe errors in the interpolation due to different point positioning.
Outcomes
The students had sufficient time to learn, collect and analyze the data, especially given that there was a week between our 3 hour lab sessions. The students performed well, though they did not go very far in their verbal descriptions. The exercise needs to explicitly demand that the students address each point in full.
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