# Vehicle Distance Measurement Method of Two-Way Two-Lane Roads Based on Monocular Vision
## 3 Experiments and Discussions
### Distance Measurement Experiment and Analysis of Results
The output effect of the model is shown in Figure 9; the model can clearly and intuitively output the detection results, classification results, and ranging results of the forward vehicle and opposite vehicle. In order to verify the feasibility and accuracy of the improved geometric ranging method, the improved geometric ranging method (method 1), the traditional geometric ranging method (method 2), and the inverse perspective mapping method [14] (method 3) are used to measure the same distance, and the ranging results were compared and analyzed. The results of the distance measurement experiment are shown in Table 4.  
It can be seen from Table 4 that the model can realize vehicle detection and vehicle classification, and distance measurement for forward and opposite vehicles within 120 m. In order to observe the change of data in the table more intuitively, the part of distance measurement in the table was drawn into a curve, as shown in Figure 10. Figure 10 shows the comparison of the ranging results. As the actual distance increased, the ranging results of the three methods were less than the actual value, and the degree of deviation from the actual value gradually increased. This is due to the fact that the pixel area occupied by the \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Vehicle Category**} & \multicolumn{3}{c}{**Distance Measurement**} \\ \cline{3-10} \multicolumn{1}{c}{\multirow{-2}{*}{**Serial**}} & \multicolumn{2}{c}{**Detection**} & \multicolumn{2}{c}{**Method 3**} & \multicolumn{2}{c}{**Method 2**} & \multicolumn{2}{c}{**Method 1**} \\ \cline{2-10} \multicolumn{1}{c}{**Number**} & \multirow{-2}{*}{**Ground**} & \multirow{-2}{*}{**Experimental**} & \multirow{-2}{*}{**Ground**} & \multicolumn{1}{c}{**Experimental**} & \multirow{-2}{*}{**Absolute**} & \multicolumn{1}{c}{**Experimental**} & \multirow{-2}{*}{**Absolute**} & \multicolumn{1}{c}{**Experimental**} & \multirow{-2}{*}{**Absolute**} \\  & & & & **(m)** & & & & **(m)** & & **(\%)** \\ \hline
1 & back & back & 14.7 & 15.4 & 4.76 & 13.5 & 8.16 & 14.0 & 4.76 \\
2 & back & back & 28.7 & 30.2 & 5.22 & 26.2 & 8.71 & 30.0 & 4.52 \\
3 & back & back & 38.2 & 39.3 & 2.87 & 34.2 & 10.47 & 39.2 & 2.61 \\
4 & back & back & 47.4 & 49.0 & 3.41 & 42.0 & 11.39 & 48.6 & 2.53 \\
5 & back & back & 52.3 & 51.8 & 2.68 & 45.1 & 15.57 & 54.1 & 1.31 \\
6 & front & front & 60.5 & 57.0 & 5.82 & 50.1 & 17.22 & 60.4 & 0.21 \\
7 & front & front & 71.3 & 65.5 & 8.15 & 56.5 & 20.83 & 68.6 & 3.88 \\
8 & front & front & 80.4 & 71.0 & 11.74 & 64.7 & 19.57 & 79.3 & 1.42 \\
9 & front & front & 85.8 & 73.5 & 14.38 & 64.7 & 24.66 & 79.3 & 7.66 \\
10 & front & front & 89.4 & 73.9 & 17.40 & 68 & 24.00 & 83.7 & 6.46 \\
11 & front & front & 93.1 & 77.1 & 17.13 & 69.6 & 25.23 & 85.5 & 8.15 \\
12 & front & front & 107.5 & 82 & 23.72 & 73.6 & 31.53 & 91.2 & 15.16 \\
13 & front & front & 118.3 & 90.0 & 23.98 & 80.0 & 32.41 & 99.5 & 15.94 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of distance measurement experiment. Figure 9: The effect of model output. object in the image becomes smaller, and the position of the object detection frame changes little at a long distance. However, the overall deviation of method 1 was less than that of the other two methods, and the ranging results were closer to the actual value. Figure 10b shows the comparison of ranging errors. The ranging error of method 1 was less than that of the other two methods within 0-120 m. Within 0-30 m, the ranging errors of the three methods had little difference. With the increase in the actual distance, the difference in the ranging errors of the three methods had an increasing trend.