REACH SCALE APPLICATION OF UAV+SFM METHOD IN SHALLOW RIVERS HYPERSPATIAL BATHYMETRY
Keywords: UAV, SfM, Alarm River, Hyperspatial Resolution, Near-Census River Science, Shallow Rivers Bathymetry
Abstract. Nowadays, rivers are impacted by different human activities and highly regulated. To rehabilitate these systems, spatial and process-based analyses of rivers are essential. Hydrodynamic models are sophisticated tools in this regard and instream topography is one of the most important input of these models. To represent hyperspatial topography and bathymetry in shallow rivers, UAV imagery and structure from motion may be an optimum method considering the extent of application, vegetation condition and flow quality. However, at the present there is no available workflow for applications of UAV+SfM method in riverine environments at extent of reach or higher scales. Therefore, in this study a new workflow has been presented and evaluated in Alarm River. The evaluation showed that the workflow provides 2 m/s speed for UAV while mapping flight lines with low illumination changes. Specific pattern of image acquisition in the proposed workflow leads to substantial decrease of process time. In addition, precise control of flight height and overlap of images may lead to consistent accurate results. The result of validation against rtkGNSS data points showed that the suggested workflow is capable of providing 0.01 m-resolution topographic data with an error less than 0.075 m and 95% level of confidence in clear shallow rivers.