# A Multi-Plant Height Detection Method Based on Ruler-Free Monocular Computer Vision
## 5 Discussion  
In order to meet the needs of current agriculture for plant height measurement, a monocular multi-plant height measurement method based on computer vision was proposed, and the accuracy and feasibility of the method were verified by principle and experiment. In this study, the results were analyzed as follows and conclusions were drawn:  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multicolumn{2}{c}{**Reference Distance \(\Delta h\)/cm**} & **Plant 1** & **Plant 2** & **Plant 3** & **Plant 4** & **SSR** \\ \hline \multirow{4}{*}{15} & Algorithmic measurements/mm & 246.691 & 260.766 & 226.534 & 183.569 & \multirow{4}{*}{8.896} \\  & Absolute error/mm & 3.024 & \(-\)0.567 & 0.201 & 0.902 & \\  & Absolute proportional error & 1.24\% & \(-\)0.22\% & 0.09\% & 0.49\% & \\ \hline \multirow{4}{*}{10} & Algorithmic measurements/mm & 246.112 & 259.964 & 225.494 & 183.245 & \multirow{4}{*}{8.896} \\  & Absolute error/mm & 2.445 & \(-\)1.370 & \(-\)0.840 & 0.578 & \\ \cline{1-1}  & Absolute proportional error & 1.00\% & \(-\)0.52\% & \(-\)0.37\% & 0.32\% & \\ \hline \multirow{4}{*}{5} & Algorithmic measurements/mm & 248.545 & 264.092 & 231.323 & 185.606 & \multirow{4}{*}{64.950} \\  & Absolute error/mm & 4.879 & 2.759 & 4.990 & 2.939 & \\ \cline{1-1}  & Absolute proportional error & 2.00\% & 1.06\% & 2.20\% & 1.61\% & \\ \hline \end{tabular} Note: Table 2 manual measurement value 2 is used as the baseline.  
\end{table}
Table 6: Change the reference distance measurement results.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multicolumn{2}{c}{**Camera and the Plant Distance d/cm**} & **Plant 1** & **Plant 2** & **Plant 3** & **Plant 4** & **SSR** \\ \hline \multirow{4}{*}{250} & Algorithmic measurements/mm & 212.008 & 275.541 & 239.234 & 201.487 & \multirow{4}{*}{1742.202} \\  & Absolute error/mm & \(-\)41.659 & \(-\)1.126 & 0.900 & 2.154 & \\  & Absolute proportional error & \(-\)16.42\% & \(-\)0.41\% & 0.38\% & 1.08\% & \\ \hline \multirow{4}{*}{300} & Algorithmic measurements/mm & 210.654 & 276.181 & 236.430 & 200.371 & \multirow{4}{*}{1855.007} \\  & Absolute error/mm & \(-\)43.012 & \(-\)0.485 & \(-\)1.903 & 1.038 & \\ \cline{1-1}  & Absolute proportional error & \(-\)16.96\% & \(-\)0.18\% & \(-\)0.80\% & 0.52\% & \\ \hline \end{tabular} Note: Table 1 manual measurement value 1 is used as the reference.  
\end{table}
Table 4: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multicolumn{2}{c}{**Camera and the Plant Distance d/cm**} & **Plant 1** & **Plant 2** & **Plant 3** & **Plant 4** & **SSR** \\ \hline \multirow{4}{*}{200} & Algorithmic measurements/mm & 254.103 & 285.824 & 238.179 & 201.508 & \multirow{4}{*}{88.808} \\  & Absolute error/mm & 0.437 & 9.158 & \(-\)0.154 & 2.175 & \\  & Absolute proportional error & 0.17\% & 3.31\% & \(-\)0.06\% & 1.09\% & \\ \hline \multirow{4}{*}{250} & Algorithmic measurements/mm & 252.008 & 284.200 & 234.441 & 197.556 & \multirow{4}{*}{77.814} \\  & Absolute error/mm & \(-\)1.659 & 7.534 & \(-\)3.892 & \(-\)1.777 & \\ \cline{1-1}  & Absolute proportional error & \(-\)0.65\% & 2.72\% & \(-\)1.63\% & \(-\)0.89\% & \\ \hline \multirow{4}{*}{300} & Algorithmic measurements/mm & 251.564 & 281.564 & 231.384 & 196.583 & \multirow{4}{*}{84.262} \\  & Absolute error/mm & \(-\)2.102 & 4.897 & \(-\)6.950 & \(-\)2.750 & \\ \cline{1-1}  & Absolute proportional error & \(-\)0.83\% & 1.77\% & \(-\)2.92\% & \(-\)1.38\% & \\ \hline \end{tabular} Note: Table 1 manual measurement value 1 is used as the reference.  
\end{table}
Table 5: Measurement results under filling light condition.