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ON THE PRECISION, ACCURACY, AND UTILITY OF OBLIQUE AERIAL PHOTOGRAMMETRY (OAP) FOR ROCK SLOPE MONITORING AND ASSESSMENT
Session: Landslides and Slope Stability II / Mouvements de terrain et stabilité des pentes II
Dave Gauthier, BGC Engineering (Canada)
Jean Hutchinson, Queen's University (Canada)
Matthew Lato, BGC Engineering (Canada)
Tom Edwards, CN (Canada)
Chris Bunce, CP Rail (Canada)
David Wood, DFWCL (Canada)
In this paper we summarize our experience in testing and refining various applications of oblique aerial ‘structure from motion’ photogrammetry to rock slope monitoring and assessment. We tested this method at a number of Canadian railway rock slope sites using both autonomous-UAV and handheld-helicopter photography of steep, otherwise inaccessible rock slopes. We demonstrate that change-detection between detailed 3D slope models acquired at different times is possible, with lower detection limits in the range of 0.5-1m3 given careful data collection and processing. We explore the precision and accuracy of this method, and demonstrate that both are comparable to other 3D remote sensing methods. While the advantages of this approach are rapid deployment at sites not amenable to other sensors, the limitations are in detection of small deformations, and uncertainties in the scale problem, which is ubiquitous in photogrammetric approaches.
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