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Oblique UAS imagery and point cloud processing for 3D rock glacier monitoring
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Resumo(s)
Rock glaciers play a large ecological role and are heavily relied upon by local communities for water, power, and revenue. With climate change, the rate at which they are deforming has increased over the years and is making it more important to gain a better understanding of these geomorphological movements for improved predictions, correlations, and decision making. It is becoming increasingly more practical to examine a rock glacier with 3D visualization to have more perspectives and realistic terrain profiles. Recently gaining more attention is the use of Terrestrial Laser Scanners (TLS) and Unmanned Aircraft Systems (UAS) used separately and combined to gather high-resolution data for 3D analysis. This data is typically transformed into highly detailed Digital Elevation Models (DEM) where Differences of DEM (DoD) is used to track changes over time. This study compares these commonly used collection methods and analysis to a newly conceived multirotor UAS collection method and to a new point cloud Multiscale Model to Model Cloud Comparison (M32C) change detection seen from recent studies. Data was collected of the Innere Ölgrube Rock Glacier in Austria with a TLS in 2012 and with a multirotor UAS in 2019. It was found that oblique imagery with terrain height corrections, that creates perspectives similar to what the TLS provides, increased the completeness of data collection for a better reconstruction of a rock glacier in 3D. The new method improves the completeness of data by an average of at least 8.6%. Keeping the data as point clouds provided a much better representation of the terrain. When transforming point clouds into DEMs with common interpolations methods it was found that the average area of surface items could be exaggerated by 2.2 m^2 while point clouds were much more accurate with 0.3 m^2 of accuracy. DoD and M3C2 results were compared and it was found that DoD always provides a maximum increase of at least 1.1 m and decrease of 0.85 m more than M3C2 with larger standard deviation with similar mean values which could attributed to horizontal inaccuracies and smoothing of the interpolated data.
Descrição
Dissertation submitted in partial fulfilment of the requirements for the degree of Master of Science in Geospatial Technologies
Palavras-chave
Change Analysis Climate Change Drone Glacier Tracking M3C2 Multirotor UAS Oblique Imagery Photogrammetry