# 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  
To assess the applicability of the new proposed method in natural rivers, a verification experiment is conducted at Panxi hydrology station, located in Huaning County, Yuxi City, Yunnan Province, where the banks are irregular, there are many rocks at the bottom of the river, and vortices are generated in some areas of the water surface. According to the years of measurement experience of the hydrology station, the velocity coefficients of the left and right banks are 0.80 and 0.70, respectively, and the surface velocity coefficient is 0.88. As shown in Figure 11, the ground calibration points, marked with red boxes A, B, C, and D, are set on both sides of the river, and E to F is designed as the cross-section line; the five yellow solid points are velocimetry points, which are set at the distances 35 m, 40 m, 45 m, 50 m, 55 m away from point E, respectively, and named as No. 1 to No. 5 in turn. Furthermore, the yellow velocimetry lines are arranged at equal intervals along the direction of water flow. A Hikvision DS-2 DC1225-I3/I5 camera is used to record a 15 s river video at 25 frames per second from a location that is 13.1 m away from point A, 4.5 m away from point B, 36.4 m away from point C, and 44.8 m away from point D. Table 8 provides a detailed presentation of the cross-section data and the measurements recorded by the LS25-1 current meter. The measured results of the comparison experiments conducted by different methods at the  
Figure 11: Ground calibration points and velocimetry lines in Panxi. same time period and the calculated errors compared with the true values of LS25-1 are presented in Table 9. Figure 12 displays the comparison of different methods. It can be concluded from the experimental data that the discharge and mean velocity measured by the proposed method are 153.59 m\({}^{3}\)/s and 1.06 m/s, respectively. When compared to the true values of the current meter, the absolute and relative errors of discharge are 5.41 m\({}^{3}\)/s and 3.40%, and the absolute and relative errors of mean velocity are 0.04 m/s and 3.64%. The accuracy of these measurements surpasses that of the GTM, FFT, and FD-DIS-G methods. As depicted in Figure 12a, there is significant fluctuation in the measured values of the vertical flow velocity measured by GTM, FFT, and FD-DIS-G at each velocity measurement point, and the vertical mean velocity measured by the new method has a very high consistency with the measured results of the current meter, and the relative errors are within 12%, with a maximum error of 11.70%. At the middle three velocimetry points, the absolute errors of vertical mean velocity are 0.03 m/s, 0.01 m/s, and 0.04 m/s, with relative errors of 2.17%, 0.75%, and 3.88%, respectively. The error fluctuations are the most minimal, indicating an overall superior performance. However, the velocimetry points close to the banks are affected by the lens aberration of the camera equipment, which makes the errors relatively large and is not conducive to improving measurement accuracy. Nonetheless, even in these cases, the measurement errors are still lower than those of the other three methods.