Introduction to Terrestrial Laser Scanning

Summary

In spring 2020, the world was hit by a pandemic that spread globally by March, causing universities and most of the world to move to remote means. Summer field camps, long hailed as a rite of passage in the geosciences, were cancelled throughout the US. The community moved quickly, with NAGT developing remote learning tools and arranging for sharing and collaboration between instructors and institutions. As such, UNAVCO (GETSI) and University of Northern Colorado embarked on a data collection campaign for a summer field course entitled "Geoscience Field Issues Using High-Resolution Topography to Understand Earth Surface Processes" – originally slated for in-person teaching. The team collected GNSS data, drone imagery for use in structure from motion (SfM), and terrestrial laser scanning (TLS) from a site near Greeley, Colorado on the Poudre River. In this assignment, students analyze TLS data in a similar manner as previously done for the SfM unit conducted previously in the course. Students compare and contrast the SfM and TLS datasets.

Day 7 - This activity is part of the 2-week remote field course Geoscience Field Issues Using High-Resolution Topography to Understand Earth Surface Processes

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Context

Audience

This exercise is intended for majors-level geoscience courses that have field or remote (online) field components.

Skills and concepts that students must have mastered

This exercise was completed after the SfM assignments in the first portion of the course. If this were done before the SfM portion or in absence of the SfM portion, an emphasis on point cloud data, geospatial data, and a background in geomorphology and/or physical geography concepts is helpful.

How the activity is situated in the course

This is situated after the first week of SfM activities, as outlined in the Sheep Draw Vignette and the course page. As such, students have been introduced to point cloud data and associated post-processing techniques. The next activities quantify the differences between the datasets with point cloud and raster differencing techniques.

Activity Length

The instructor gives a lecture (~45 mins) on TLS methods such as from "Unit 1-TLS: Introduction to TLS". The instructor introduces the assignment, then students work independently to complete the TLS assignment. As with the SfM unit, students focus on either area 1 or area 2. This activity takes students about four hours. An office hour or class check-in to trouble shoot after some independent effort would be appropriate.

Goals

Content/concepts goals for this activity

Analyze TLS data and compare with SfM data

Higher order thinking skills goals for this activity

Compare and contrast spatial datasets and evaluate pros and cons of data collection for different situations.

Other skills goals for this activity

Quantify geomorphic features with TLS data

Description and Teaching Materials

This exercise uses pre-collected TLS data and students are asked to compare and contrast this dataset with the previously-created SfM dataset, collected for the same geographic location on the same day. Students visually inspect the datasets for similarities and differences. As with the SfM activity, students measure geomorphic features in the scene and compare their measurements for the two methods. Using skills gained in previous class activities, students classify the TLS cloud into vegetation and ground, export the ground cloud as a text file, and create a raster that matches the specifications of the one made in the SfM activity.


Sheep Draw Vignette (Microsoft Word 2007 (.docx) 2MB Dec14 20)
Intro Site Video (MP4 Video 56.8MB Dec14 20)
TLS Methods Video (MP4 Video 143.5MB Dec14 20)
Student Intro to TLS Activity (Microsoft Word 2007 (.docx) 38.2MB Dec14 20)

Link to UNAVCO TLS Poudre at Sheep Draw Point Cloud

Technology Needs

A computer with CloudCompare installed is required.

Teaching Notes and Tips

The TLS dataset is dense, but patchy. Students will notice the incompleteness of the dataset. It may be worthwhile to show a TLS dataset more suited to the application. In this case, the SfM dataset is more robust and captures the geomorophic features of the river more effectively than TLS.

Assessment

As the summative assessment, students answer questions about differences between the TLS and SfM dataset. Formative assessment should be done through discussion with students as a whole group or individually.

References and Resources



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