Abstract
Field measurement of water level is important for water conservancy project operation and hydrological forecasting. In this study, we proposed a new measuring technique by integrating the advantages of unmanned aerial vehicle (UAV) photogrammetry and image recognition technology. Firstly, the imagery of water fluctuation process was captured by an UAV airborne camera, and water surface line in the imagery was recognized and extracted using image recognition technology. Subsequently, successive water levels at a measuring section were calculated by parameter calibration. Statistical parameters of water levels, such as maximum, average, and minimum values during the capturing period were also calculated. Additionally, we introduced a correction method to offset the error caused by UAV drift. The newly proposed method was tested in field measurement for Miaowei hydropower station, China, and the results showed that the method is reliable and adoptable.
Highlights
Water level process of water conservancy projects (e.g., Oroville dam, USA; Three Gorges Dam, China, etc.), overcurrent structures, and rivers is one of the important hydraulic indexes
The water level offset displacements that are caused by unmanned aerial vehicle (UAV) drift in each frame are traced
The UAVi-fmwl theory and implementation processes are as follows: (1) capture the video of water surface fluctuation processes, (2) dedicate image processing software orderly preprocess images separated from video captured by airborne camera, (3) segment the water body and background, (4) use the traversal algorithm to calculate the pixel coordinates of measurement section, and (5) obtain the actual water level at that time according to the conversion coefficient and the conversion relationship
Summary
Water level process of water conservancy projects (e.g., Oroville dam, USA; Three Gorges Dam, China, etc.), overcurrent structures (e.g., spillway, lock approach, and plunge pool, etc.), and rivers is one of the important hydraulic indexes. For newly constructed dams and river engineering works, it is necessary to conduct accurate field measurements of water level and its surface fluctuations in order to analyze their operation behaviors, test engineering design, and provide operation guidance. The high-precision measurement of water level is significant for the safe operation of water conservancy projects [1]. Instruments for field measurement of water level should be advanced and automatic with the premise of reliability, economy, durability, and practicality [1]. Common instruments include water level measuring rule, float-type water level gauge, pressure-type water level gauge, ultrasonic water level gauge, and radar water level gauge. These instruments have some disadvantages, especially in the complex natural environment, details are as follows
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