Initial Publication Date: February 13, 2018
David Schmidt & Knut Christianson: Using Analyzing High Resolution Topography with TLS and SfM in Field Methods in Remote Sensing at University of Washington-Seattle Campus
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Provenance: Beth Pratt-Sitaula, EarthScope Consortium
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About this Course
Upper division elective for geology undergraduates
16
students
4 hours per week
of class time over 10 weeks for the entire course.
Syllabus (Acrobat (PDF) 75kB Jul27 17)
An introduction to various field sensors that remotely capture the morphology and surface properties of the landscape, and discusses how to process these data for various products, including the generation of digital elevation models and change detection.
Through a series of field and laboratory exercises, students will: 1) learn how to collect, process, and interpret data from several field-based sensors, such as terrestrial laser scanners (TLS), optical cameras, terrestrial radar interferometers, and ground-penetrating radars (GPR); 2) understand the tradeoffs between using different sensors, and gain insight into how to optimally pair a sensor to an application; and 3) learn how to document and discuss a data set through the preparation of written scientific reports.
We implemented a quarter-long field methods course that introduced students to a range of field instruments. TLS and SfM represented two of the four field-based methods that were introduced in the course. This was a hands-on course for the students, with considerable time spent working in the computer lab performing operations on real data. About half of the students had previously taken a formal remote sensing course that focused more on satellite-based imagery. So this course complemented their previous experiences, and expanded into field-scale imagery and change detection.
The students appreciated this introduction to new technologies, and enjoyed the opportunity to compare products from multiple techniques.
Our Experience Teaching with GETSI Materials
The module was restructured to fit within a quarter-system class and conform with the course schedule. Specific questions and expectations were tailored to the chosen field target. We choose to emphasize change detection so we used Unit 1-TLS and Unit 1-SfM to introduce the methods and then used elements of Units 4 & 5 for the combined field work and summative assessment.
Relationship of GETSI Materials to our Course
This was a quarter-long course with class time scheduled in 2-hour blocks twice per week (4 hours per week of in-class contact time). Each section of the course focused on a different instrument or technique, with each covering a 2-3 week span. Students were first introduced to the concept of digital elevation models, and their utility in the study of geological processes. This was followed by a conceptual overview of each technique. Laboratory work helped to build a basic comfort level with the software packages using pre-collected data sets. A subsequent lab assisted the students in analyzing data collected during a field trip and in preparing the products for a summary report.
Unit 1 TLS and SfM
- Over a 1-month period, we did Unit 1 for both methods in this module--TLS and SfM. For each we included a series of lectures that covered the conceptual background of the technique, and reviewed various examples to show how the method and data products can be used to solve geological problems. Several informal surveys were conducted on campus during class time for students to see how the surveys are implemented. A weekly computer laboratory, where they worked through a prepared data set, helped students to gain familiarity with the relevant software packages (RiScan Pro and Agisoft PhotoScan) and the data products (points cloud and DEMs). GETSI materials were provided as reference materials.
Unit 4 & Unit 5 (Change Deception and Summative Assessment)
- After the students understood the basics of both methods we conducted a 1-day field trip to local beach bluff for which we had TLS data from two years previous. The goal was to see if we could detect erosion over that period and assess the different between using TLS and SfM for this site and application.
- Students were asked to prepare a summary report that documented the data collection, analysis, and interpretation of erosion on a coastal bluff. The point cloud data set of the bluff from 2 years earlier was provided to the students, which provided the opportunity for change detection. The students were tasked with the following questions:
- How quickly is the coastal bluff eroding?
- Is the erosion uniform across the bluff?
- What geological processes are active?
- The field site and situation presented some challenges that were valuable learning experiences for the students, although less than ideal for data collection. It started to rain partway through the field trip, which can impact quality for both methods. The tide started to come in, limiting the scanner location possibilities.
- The time allocated for each section of the course included a 1-day field trip for data collection, 1 week of data analysis (~4 hours of class time) on an example data set, and 1 week of report preparation (~4 hours of class time) on the newly-collected data set. The students were also instructed to keep detailed field and lab notes. We used a University-owned TLS and digital SLR camera. The students submitted a first full draft that was returned with detailed comments by the instructors (on both the writing and content). The students then had one week to make revisions and submit a final version.
Assessments
The primary assessment was from laboratory assignments and the summative report on the bluff site. Students were are also given a midterm exam that focused on the theoretical and practical concepts of TLS and SfM.
Outcomes
The ultimate goal was to develop the students' ability to design a field experiment and perform an analysis of real data, taking into account the limitations and uncertainties of the data. A secondary goal was to expose students to various new technologies, and illustrate how high-resolution field data can be used to answer geological questions. The module accomplished the goals of exposing students to sensor technologies and workflows. The students demonstrated a basic understanding of the capabilities of the instruments and how they can be applied. However, they likely did not yet gain the proficiency to conduct an independent investigation.
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