# Estimation of River Velocity and Discharge Based on Video Images and Deep Learning
## 3 Results and Discussion
### Experiments in the Measurement of River Velocity and Discharge
#### 3.3.2 Experiment in Natural Rivers
A 20 s river video is recorded at a frame rate of 25 frames per second to capture the flow characteristics in detail. The velocity coefficient of the bank is 0.70, and the surface velocity coefficient is 0.90. Figure 13 shows the layout of the ground calibration points A, B, C, and D, as well as the 10 velocity-measuring lines, and EF is regarded as the cross-section line; E is the starting point, while F is the end point. The measured points named as No. 1 to No. 10 in turn are positioned at intervals of 4 m, as shown in the yellow solid points in the figure. Table 10 presents the cross-section data and the true values obtained from the LS25-3A current meter at the velocimetry points. Table 11  
Figure 12: The results and analysis of different methods. (**a**) Results of the vertical mean velocity; (**b**) comparison of running time; (**c**) results and errors of total discharge; (**d**) results and errors of mean velocity. provides a comparative analysis of the measured results and the errors associated with several methods, including the proposed one. The measurement results of the proposed method have proven to be the most precise. Specifically, the measured total discharge is 86.11 m\({}^{3}\)/s with a relative error of 2.37%, which is 10.31% and 6.14% higher than that of GTM and FFT. In terms of mean velocity, the relative error of the proposed method is only 1.87%, which is 10.28% and 6.54% lower than that of other methods, respectively, and its stability and accuracy are improved to a great extent. It is noted that the error of vertical mean velocity at the last velocimetry point reaches 104.76%, which is because the point is far away from the lens, and the flow field near the bank is chaotic, resulting in the generated space-time images of the river having more noise components and less effective texture information, whereas the relative errors at the remaining measurement points are all controlled within 28%. Although the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Points**} & **Starting** & \multirow{2}{*}{**Depth/(m)**} & **Vertical Mean** & **Partial Mean** & **Partial Area/(m\({}^{2}\))** & **Partial Discharge/(m\({}^{3}\)/s)** \\  & **Distance/(m)** & & & & & \\ \hline \multirow{4}{*}{No. 1} & 18.1 (shore) & & & 0.32 & 7.13 & 2.28 \\  & 21-24 & & & 0.45 & & 0.70 & 7.72 & 5.40 \\  & 24-28 & & & & 1.12 & 7.84 & 8.78 \\  & 28-32 & & & & 1.34 & 8.04 & 10.80 \\  & 32-36 & & & & 1.39 & 7.60 & 10.60 \\  & 36-40 & & & & 1.38 & 7.36 & 10.20 \\  & 40-44 & & & & 1.38 & 7.36 & 10.20 \\  & 44-48 & & & & 1.36 & 7.24 & 9.85 \\  & 48-52 & & & & 1.38 & 7.36 & 10.20 \\  & 52-56 & & & & 1.30 & 7.76 & 10.10 \\  & 56 & 2.01 & 1.21 & & & \\  & 56-60 & & & & 0.92 & 7.68 & 7.07 \\  & 60-63 & & & & 0.44 & 6.63 & 2.92 \\  & 64.5 (shore) & & & & & \\ \hline \multicolumn{6}{l}{Cross-section area/(m\({}^{2}\)): 82.40} \\ \multicolumn{6}{l}{Discharge/(m\({}^{3}\)/s): 88.20} \\ \multicolumn{6}{l}{Mean velocity/(m/s): 1.07} \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Data of cross-section and the LS25-3A current meter. Figure 13: Ground calibration points and velocimetry lines in Mengxing. measured errors of the vertical mean velocity of the GTM and FFT methods are lower than those of the new proposed method at certain points, the overall measurement effect of these two methods is not ideal. The comprehensive analysis of three sets of experimental results indicates that the proposed method can realize reliable measurement and has good stability, and the development of this technology makes it possible for STIV technology to be more widely used and popularized in the monitoring of velocity.