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TitleTowards precise drone-based measurement of elevation change in permafrost terrain experiencing thaw and thermokarst
AuthorFraser, R HORCID logo; Leblanc, S GORCID logo; Prevost, C; van der Sluijs, J
SourceDrone Systems and Applications 2022 p. 1-28, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20220133
PublisherCanadian Science Publishing
Mediapaper; digital; on-line
File formatpdf
SubjectsScience and Technology; Nature and Environment; permafrost; thermokarst; subsidence; drones; elevations
Illustrationstables; photographs; charts; diagrams
ProgramCanada Centre for Remote Sensing Remote Sensing Science Program - Optical methods and applications
Released2022 10 05
AbstractMeasuring 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.
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.

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