A Comparison of Hydraulic Modeling Results between Unmanned Aerial Vehicle with Structure-from-Motion and LIDAR Produced Digital Elevation Models



Zahirieh, Sherwin

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Current traditional methods of gathering topographic data for hydraulic modeling can be time consuming and costly. One potential method to gather topographic data in a more timely and costly efficient manner is the use of unmanned aerial vehicles (UAVs) and structure-from-motion (SfM) image processing. This thesis describes the comparison of Digital Elevation Models (DEM) generated from LIDAR and from Structure-from-Motion and Unmanned Aerial Vehicles and the results of open channel hydraulic modeling based on these models. Unlike LIDAR, UAV+SfM topographic modeling is both time and cost efficient. However, it is still necessary to study the accuracy of its model results in comparison to traditional LIDAR models. Using Agisoft Photoscan, photos from the UAV were converted into DEM through the structure-from-motion process. The two different DEMs were then used in the HEC-RAS hydraulic model. By examining several different flows through both cross-sections, the wetted area and floodplain areas for different study sites were calculated. By analyzing the differences in elevations, channel areas, and floodplain areas between the two models, the accuracy was determined. Under the assumption that LIDAR data are correct, the results indicate that the UAV+SfM method has the promise of developing similar topographic data models compared to LIDAR, but not with enough accuracy to use in place of LIDAR given the differences in areas between the two sources.



Unmanned Aerial Vehicles, Structure-from-motion, Surveying, Rivers, Floodplain mapping