| Title | Towards precise drone-based measurement of elevation change in permafrost terrain experiencing thaw and thermokarst |
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| Author | Fraser, R H ;
Leblanc, S G; Prevost, C; van der Sluijs, J |
| Source | Drone Systems and Applications 2022 p. 1-28, https://doi.org/10.1139/dsa-2022-0036  Open Access |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20220133 |
| Publisher | Canadian Science Publishing |
| Document | serial |
| Lang. | English |
| Media | paper; digital; on-line |
| File format | pdf |
| Subjects | Science and Technology; Nature and Environment; permafrost; thermokarst; subsidence; drones; elevations |
| Illustrations | tables; photographs; charts; diagrams |
| Program | Canada Centre for Remote Sensing Remote Sensing Science Program - Optical methods and applications |
| Released | 2022 10 05 |
| Abstract | Measuring ground elevation changes plays a crucial role in several environmental applications. For instance, permafrost soils undergo seasonal active layer freezing and thawing that causes cyclic
elevation changes. Permafrost thaw can result in unidirectional ground subsidence, which may be gradual and uniform, or rapid and irregular in the case of thermokarst landforms such as slumps and degrading ice-wedges. Photogrammetric drone surveys
have effectively characterized large (> 0.1 m) ground elevation changes resulting from thermokarst, yet many permafrost processes of interest lead to more subtle elevation changes. In this study, we assessed various drone-based surveying strategies
for their precision to measure smaller (< 0.1 m) ground elevation changes to better characterize permafrost-driven surface dynamics. The strategies were compared by examining the short-term reproducibility of modeled elevation for 76 bare ground
targets, derived from six repeat drone surveys captured under variable illumination. We found that the Phantom 4 RTK drone using direct georeferencing, combined with one fixed GCP, could reproduce elevations with a mean absolute deviation of 0.6 cm,
suggesting a minimum level of change detection of 1.4 cm at 95% confidence. Drone-based methods for measuring permafrost elevation changes should be complementary to in situ and satellite-based (e.g. differential interferometric SAR) approaches.
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| Summary | (Plain Language Summary, not published)
Permafrost ground undergoes cyclical annual elevation changes due to the freezing and thawing of ground water. Permafrost terrain may also decrease in
elevation due to the local and irregular melting and removal of ground ice that provides structural support. These thaw-driven surface changes can negatively effect northern infrastructure, ecosystems, and water quality. In this study, we assessed
the ability to use a mapping drone and structure-from-motion processing to detect small (< 10 cm) elevation changes occurring in bare ground. We found that, in six repeat drone surveys, the modeled elevation for 76 bare, stable targets deviated by
only 0.6 cm on average, implying that elevation changes as small as 1.4 cm could be reliably detected. These techniques will now be tested in a permafrost environment and compared to complementary measurement techniques made at single points using
ground instruments and at regional scales using synthetic aperture radar (SAR) satellite measurements. |
| GEOSCAN ID | 330264 |
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