# An Image Processing Method for Measuring the Surface Area of Rapeseed Pods
## 3 Results and Analysis
### Analysis of the Accuracy of Measurement
#### 3.1.2 Comparison of the Results of the Other Four Measurement Methods with the 3-D Method
\begin{table}
\begin{tabular}{l c c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**The Model Established with the Modeling Samples**} & \multicolumn{6}{c}{**Accuracy Analysis of the Testing Samples**} \\ \cline{2-11}
**Experiment** & **Number** & \multicolumn{2}{c}{**The Average**} & \multicolumn{2}{c}{**The Average**} & \multicolumn{2}{c}{**The Average**} & \multicolumn{2}{c}{**The Average**} & \multicolumn{2}{c}{**The Average**} \\
**of** & **Measurement** & **Measurement Value of** & **Correlation** & **Number of** & **Measurement Value** & **Measurement Value of** & **Relative** & **RMSE (cm\({}^{2}\))** \\  & **Samples** & **Value of the 3-D** & **the Image Processing** & **Coefficient** & **Samples** & **of the 3-D Method** & **the Image Processing** & **Error** & **(cm\({}^{2}\))** \\  & & **Method (cm\({}^{2}\))** & **Method (cm\({}^{2}\))** & **Method (cm\({}^{2}\))** & **Method (cm\({}^{2}\))** & **Method (cm\({}^{2}\))** & **Method (cm\({}^{2}\))** & **Method (cm\({}^{2}\))** \\ \hline Replicate 1 & 54 & 8.44 & 10.25 & 0.92 **\%** & 27 & 8.42 & 8.74 & 3.78\% & 0.95 \\ Replicate 2 & 54 & 8.46 & 10.47 & 0.91 **\%** & 27 & 8.39 & 8.25 & 1.67\% & 0.89 \\ Replicate 3 & 54 & 8.40 & 10.41 & 0.91 **\%** & 27 & 8.49 & 8.33 & 1.93\% & 0.93 \\ Average & 54 & 8.43 & 10.38 & 0.92 **\%** & 27 & 8.43 & 8.44 & 2.46\% & 0.92 \\ \hline \hline \end{tabular} Note: The model established with the modeling samples: A total of 54 pools from different sizes of two repeated plants were randomly selected from each plot as modeling samples. The surface area of pools was measured by 3-D and image processing methods, respectively. The values measured by the two methods were analyzed by regression analyses and a correction model was established. An analysis of the accuracy of the testing samples was performed as follows at least 27 pools with different sizes of another repeated plant in each plot were used as test samples. The surface area of pools was measured using a 3-D method and image processing, respectively, and then the correction model was used to correct the measured value of the image processing method. The corrected value was compared with the measured value of the 3-D method, i.e., an accuracy analysis. “mers significant test \(<\) 0.01.  
\end{table} 
Table 1: Analysis of the accuracy of results measured by the image processing method. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Experiment**} & **Number of** & \multicolumn{2}{c}{**The Average**} & \multicolumn{2}{c}{**Clark Formula Method**} & \multicolumn{2}{c}{**Long Formula Method**} & \multicolumn{2}{c}{**Flattening Scanning Method**} & \multicolumn{2}{c}{**Quasi-Cylinder Side Area Method**} \\ \cline{3-14}  & **Samples** & **Measurement** & **Relative** & **RMSE** & **The Average** & **The Average** & **The Average** & **The Average** & **The Average** & **The Average** & **Relative** & **RMSE** & **The Average** & **Relative** & **RMSE** \\  & **Method (cm\({}^{2}\))** & **Method (cm\({}^{2}\))** & **Error (cm\({}^{2}\))** & **Value (cm\({}^{2}\))** & **Error (cm\({}^{2}\))** & **Error (cm\({}^{2}\))** & **Value (1.3 Comparison of the Results of Measurement Obtained by the Image Processing Method with Those of the Other Four Methods of Measurement  
The same test samples were measured using image processing and the other four measurement methods described above, and the results were analyzed comparatively. The corresponding values of the relative error and the RMSE of measurement (reflecting the degree of dispersion) of the image processing method were lower than those of the other four methods. They were also approximately 14.07% and 0.72 cm\({}^{2}\) lower than those of the flattening scanning method, which was the most accurate of the four measurement methods. Therefore, the accuracy was much higher when the image processing method was used when compared to the other four measurement methods.