Abstract
An automated, fixed-location, time lapse camera system was developed as an alternative to monitoring geological processes with lidar or ground-based interferometric synthetic-aperture radar (GB-InSAR). The camera system was designed to detect fragmental rockfalls and pre-failure deformation at rock slopes. It was implemented at a site along interstate I70 near Idaho Springs, Colorado. The camera system consists of five digital single-lens reflex (DSLR) cameras which collect photographs of the rock slope daily and automatically upload them to a server for processing. Structure from motion (SfM) photogrammetry workflows were optimized to be used without ground control. An automated change detection pipeline registers the point clouds with scale adjustment and filters vegetation. The results show that if a fixed pre-calibration of internal camera parameters is used, an accuracy close to that obtained using ground control points can be achieved. Over the study period between March 19, 2018 and June 24, 2019, a level of detection between 0.02 to 0.03 m was consistently achieved, and over 50 rockfalls between 0.003 to 0.1 m3 were detected at the study site. The design of the system is fit for purpose in terms of its ground resolution size and accuracy and can be adapted to monitor a wide range of geological and geomorphic processes at a variety of time scales.
Highlights
Terrestrial remote sensing technologies, such as terrestrial laser scanning (TLS) and structure from motion (SfM) photogrammetry have been increasingly used to characterize and monitor rock slope hazards [1,2,3,4], and other geomorphic processes [5,6,7,8,9]
A five-camera time lapse camera system was implemented for the long-term monitoring of a rock slope, and an automated data processing workflow was developed that does not require ground control points
This study shows that monitoring using a low number of camera positions in a fixed setup is best done with a network of ground control points
Summary
Terrestrial remote sensing technologies, such as terrestrial laser scanning (TLS) and structure from motion (SfM) photogrammetry have been increasingly used to characterize and monitor rock slope hazards [1,2,3,4], and other geomorphic processes [5,6,7,8,9]. They are used to monitor processes at repeat intervals on the order of days to months or years, wide spread use as fixed or permanent installation systems has yet to be achieved. It produces a more accurate Magnitude-Frequency (M-F) relationship as compared to measuring at longer time intervals [16,17]
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